The whole of the tissue of the plant is formed by the division of this apical cell.

In the polyp the nervous tissue is always in the form of a scattered plexus, never concentrated to form a definite nervous system as in the medusa.

You were lucky and there was no torn tissue or fractures.

A small packet wrapped in tissue fell to her lap.

Next the larvae make their way into the connective tissue in the pro-thorax, and ultimately bore a channel into the base of the piercing apparatus and come to rest between the hypopharynx and the labium.

The ectoderm furnishes the general epithelial covering of the body, and the muscular tissue, nervous system and sense-organs.

Vacuolated tissue of pharyngeal wall, the so-called " pleurochords " of Masterman.

Pulling out a tissue he handed it to her.

Carmen wiped Destiny's face and eyes with the cool rag and used a tissue to wipe her nose.

Opening it, she removed a tissue and wiped the tears from her face.

And the botanist who finds that the apple falls because the cellular tissue decays and so forth is equally right with the child who stands under the tree and says the apple fell because he wanted to eat it and prayed for it.

Filaria medinensis - the Guinea worm - is parasitic in the subcutaneous connective tissue of man (occasionally also in the horse).

She grabbed a tissue from the box on the counter and blew her nose.

This one slid through the lemon like it was tissue paper and pricked her finger on the other side.

of the cell-wall (which is secreted by the living cell-body) the protoplasm dies, and a tissue in which this has occurred consists solely of the dead framework of cell-walls, enclosing in the cavities, originally occupied by the protoplasm, simply water or air.

The nervous system of the medusa consists of sub-epithelial ganglion-cells, which form, in the first place, a diffuse plexus of nervous tissue, as in the polyp, but developed chiefly on the subumbral surface; and which are concentrated, in the second place, to form a definite central nervous system, never found in the polyp. In Hydromedusae the central nervous system forms two concentric nerverings at the margin of the umbrella, near the base of the velum.

I found surprises, not in the stocking only, but on the table, on all the chairs, at the door, on the very window-sill; indeed, I could hardly walk without stumbling on a bit of Christmas wrapped up in tissue paper.

She daubed her eyes with a tissue and swallowed a sob - if she could speak the words.

She snatched a tissue from the jeweled box on her desk and buried her nose into its softness.

In all cases, while the internal threads which bear the cortical branches consist of elongated cells with few chromatophores, and no doubt serve mainly for conduction of food substances, the superficial cells of the branches themselves are packed with chromatophores and form the chief assimilating tissue of the plant.

a meristematic (cell-dividing) region occupying the whole of a certain transverse zone of the thallus, and cutting off new cells to add to the permanent tissue on both sides.

Blowing it on a tissue, she rang the door bell.

Lori thanked her for the tissue and wiped her eyes again.

The adult worm, which is of extremely minute size, the male being only Fi l sth and the female s of an inch in length inhabits the alimentary canal of man and many other carnivorous mammalia; the young bore their way into the tissues and become encysted in the muscles - within the muscle-bundles according to Leuckart, but in the connective tissue between them according to Chatin and others.

The muscular tissue consists primarily of processes from the bases of the epithelial cells, processes which are contractile in nature and may be distinctly striated.

She plucked a tissue from the box on the counter and blew her nose.

The tentacles are always solid, containing an axis of endoderm-cells resembling notochordal tissue or plantparenchyma, and are but moderately flexible.

The tissue developed to meet the demands for conduction in such cases always shows some of the characters described.

"Linda says you can call her whenever you want," Lon said, handing Sofia a tissue with a phone number and smiley face written on it.

She frantically threw her purse open, searching for a tissue, but a violent sneeze ripped through her lungs so quickly she barely had time to cover her mouth with her hand.

She blew her nose and threw the tissue in the trash.

external epithelium is flat on the ex-umbral surface, more columnar on the sub-umbral surface, where it forms the muscular tissue of the sub-umbrella and the velum.

In places the nematocysts may be crowded so thickly as to form a tough, supporting, " chondral " tissue, resembling cartilage, chiefly developed at the margin of the umbrella and forming streaks or bars supporting the tentacles (" Tentakelspangen," peronia) or the tentaculocysts (" Gehorspangen," otoporpae).

ia.Examples of the differentiation of the tissue of plants.

In addition to the cell types described, it is a very common occurrence in these bulky forms for rhizoid-like branches of the cells to grow out, mostly from the cells at the periphery of the medulla, and grow down between the cells, strengthening the whole tissue, as in the Rhodophyceae.

Darkyn was known for going through them like tissue paper.

The muscle-fibres arise as processes from the bases of the epithelial cells; such cells may individually become sub-epithelial in position, as in the polyp; or, in places where muscular tissue is greatly developed, as in the velum or sub-umbrella, the entire muscular epithelium may be thrown into folds in order to increase its surface, so that a deeper sub-epithelial muscular layer becomes separated completely from a more superficial bodyepithelium.

Maas in Results of In its arrangement the muscular tissue the "Albatross " Expedition, forms two s stems: the one composed Museum of Comparative Y P Zoology, Cambridge, Masse, of striated fibres arranged circularly, that U.S.A. is to say, concentrically round the central FIG.

Prolongations from the rim of chondral tissue may form clasps or peronia supporting the tentacles.

The viscid pulp soon hardens, affording a protection to the seed; in germination the sucker-root penetrates the bark, and a connexion is established with the vascular tissue of the first plant.

The properties of podophyllin resin vary with the reaction of the tissue with which it is in contact; where this is acid the drug is inert, the picro-podophyllin being precipitated.

The mesogloea in the hydropolyp is a thin elastic layer, in which may be lodged the muscular fibres and ganglion cells mentioned above, but which never contains any connective tissue or skeletogenous cells or any other kind of special mesogloeal corpuscles.

In such cases the characters of the adult tissue clearly depend solely upon the characters of the cell-walls, and it is usual in plant-anatomy to speak of the wall with its enclosed cavity as the cell, and the contained protoplasm or other substances, if present, as cell-contents.

A specialized conducting tissue of this kind, used mainly for transmitting organic substances, is always developed in plants where the region of assimilative activity is local in the plant-body, as it is in practically all the higher plants.

The cells Cell and are commonly joined end to end in simple or branched Tissue filaments.

Such a system is called a tissuesystem, the word tissue being employed for any collection of cells with common structural, developmental, or functional characters to which it may be conveniently applied.

F, Section through the surface tissue of the Brown Alga Cutleria multifida, showing the surface layer of assimilating cells densely packed with phaeoplasts.

She started to cry again and Carmen pulled a fresh tissue from her purse.

The embryo consists of an axis bearing two or more cotyledons and ending below in a radicle; it lies in a generally copious food-storing tissue (endosperm) which is the remains of the female prothallus.

In many Laminariaceae the thallus also grows regularly in thickness by division of its surface layer, adding to the subjacent permanent tissue and thus forming a secondary meristem.

Carmen grabbed a tissue from the table next to the bed and wiped Destiny's nose.

After he recovered from the stabbing, the Doctor said he had scar tissue and would be susceptible to pneumonia in the injured lung.

The guard-cells contain chlorophyll, which is absent from typical epidermal cells, the latter acting as a tissue for water storage.

It is from these cells the permanent fibrous tissue is formed.

Tears flooded her eyes and she dug in her purse for a tissue.

She sniffed and wiped her eyes with a well-used tissue.

Carmen blew her nose and grabbed another tissue.

It is probable that the parasite is then transferred to the alimentary canal of man by means of drinking-water, and thence makes its way to the subcutaneous connective tissue.

The adult stages are found in the sub-peritoneal connective tissue.

In this way we may distinguish, first, vegetative reproduction, the result of discontinuous growth of the tissues and cell-layers of the body as a whole, leading to (I) fission, (2) autotomy, or (3) vegetative budding; secondly, germinal reproduction, the result of the reproductive activity of the archaeocytes or germinal tissue.

A solid fungal body may usually be seen to consist of separate hyphae, but in some cases these are so bent and closely interwoven that an appearance like that of ordinary parenchymatous tissue is obtained in section, the structure being called pseudo parenchyrna.

The internal tissue of the body of the solid higher Fungi, particularly the elongated stalks (stipes) of the fructifications of the Agarics, consists of hyphae running in a longitudinal direction, which no doubt serve for the conduction of organic food substances, just as do the trumpet-hyphae, similar in appearance, though not in origin, of the higher Brown Seaweeds.

In the higher forms a storage and a mechanically-strengthening system may also be developed, and in some aerial Fungi an external protective tissue.

The frondose (thalloid) Jungermanniales show no such differentiation of an assimilating tissue, though the upper cells of the thallus usually have more chlorophyll than the rest.

Such differentiated water-conducting cells we call hydroids, the tissue they form hydrom.

The latter are plates of green tissue one cell thick, while the stem consists of uniform more or less elongated cylindrical cells.

In a few cases there is a special surface or epidermal layer, but usually all the outer layers of the stem are composed of brown, thick-walled, lignified, prosenchymatous, fibre-like cells forming a peripheral stereom (mechanical or supporting tissue) which forms the outer cortex.

In the highest family of mosses, Polytrichaceae, the differentiation of conducting tissue reaches a decidedly higher level.

In addition to the water-conducting tissue or hydrom there is a welldeveloped tissue (leptom) inferred to be a conducting channel for organic substances.

Besides the hydrom and leptom, and situated between them, there is a tissue which perhaps serves to conduct soluble carbohydrates, and whose cells are ordinarily full of starch.

These three concentric tissue mantles are evidently formed by the conjoined bases of the leaf traces, each of which is composed of the same three tissues.

In Cat harinea undulata the central h drom cylinder of the aerial stem is a loose tissue, its interstices being filled up with thin-walled, starchy parenchyma.

Besides this there is usually a living conducting tissue, sometimes differentiated as leptom, forming a mantle round the hydrom, and bounded externally by a more or less well-differentiated endodermis, abutting on an irregularly cylindrical lacuna; the latter separates the central conducting cylinder from the cortex of the seta, which, like the cortex of the gametophyte stem, is usually differentiated into an outer thick-walled stereom and an inner starchy parenchyma.

trace a three-fold division of tissue systems, a division of which there are indications among the lower plants, and which is the expression of the fundamental conditions of the evolution of a bulky differ- Tissue entiated plant-body.

On the other hand, we have (2) an internal differentiation of conducting tissue, the main features of which as seen in the gametophyte of Bryophytes have already been fully described.

In the Vascular Plants this tissue is collectively known as the vascular system.

The remaining tissue of the plant-body, a tissue that we must regard phylogenetically as the remnant of the undifferentiated tissu~ of the primitive thallus, but which often undergoes further different,iation of its own, the better to fulfil its characteristically vital functions for the whole plant, is known, from its peripheral position in relation to the primitively central conducting tissue, as (3) the cortex.

In a second type they are situated at the ends of tracheal strands and consist of groups of richly protoplasmic cells belonging to the epidermis (as in the leaves of many ferns), or to the subjacent tissue (the commonest type in flowering plants); in this last case the cells in question are known as epithem.

At the apex of a root, covering and protecting th~ delicate tissue of the growing point, is a special root-cap consistinf of a number of layers of tissue whose cells break down into mucilagi towards the outer surface, thus facilitating the passage of the ape~ as it is pushed between the particles of soil.

The cortex, as has been said, is in its origin the remains of th~ primitive assimilating tissue of the plant, after differentiatioi of the surface layer and the conducting system.

In the leafy shoot this function is mainly localized in the cortical tissue of the leaves, known as mesophyll, Mesophyli.

The stomata are in direct communication with the ample system of intercellular spaces which is found in the loosely arranged mesophyll (spongy tissue) on that side.

This is the main transpiring tissue, and is protected from direct illumination and consequent too great evaporation.

The main assimilating tissue, on the other hand, is under the upper epidermis, where it is well illuminated, and consists of oblong cells densely packed with chloroplasts and with their long axes perpendicular to the surface (palisade tissue).

c/i, epidermis; st stoma; me,, mesophyil; pal, palisade; spa, spongy tissue; Isp, inteicellular space; wi., water tissue; x, xylem; p/i, phioem; Phil, phloeoterma; sri, scierenchyma.

The leaves of shade plants have little or no differentiation of palisade tissue.

In fleshy leaves which contain a great bulk of tissue in relation to their chlorophyll content, the central mesophyll contains little or no chlorophyll and acts as waterstorage tissue.

In the larger veins of the leaf especially in the midrib, in the petiole, and in the young stem, a1 extremely frequent type of mechanical tissue is collenchyma.

This consists of elongated cells with cellulose walls, which are locall~ thickened along the original corners of the cells, reducing the lumer to a cylinder, so that a number of vertical pillars of cellulose con nected by comparatively thin walls form the framework of th~ tissue.

This tissue remains living and is usually formed quiti early, just below the epidermis, where it provides the first periphera support for a still growing stem or petiole.

The whole tissue system is known as the stelar system (from the way in which in primitive forms it runs through the whole axis of the plant in the form of a column).

This is a morphological term given to the particular~ type of hydrom found in both Pteridophytes and Phanerogams, together with the parenchyma or stereom, or both, included within the boundaries of the hydrom tissue strand.

The sieve-tubes, with their accompanying parenchyma or stereom, constitute the tissue called phloem.

c eun~7 Such an arrangement of vascular tissue is called radial, ~

The pericycle and mesocycle together form the conjunctive tissue of the stele in these simplest types.

When the diameter of the stele is greater, parenchymatous conjunctive tissue often occupies its centre and is frequently called the pith.

Where internal phloem is present this is separated from the internal endodermis by an endocycle or internal pericycle, as it is sometimes called, and from the xylem by an internal mesocyclethese two layers, together with the outer mesocycle and pericycle, constituting the conjunctive tissue of the now hollow cylindrical stele.

The centre of the S~hooo- stele is however often occupied by a large-celled pith resembling the cortex in structure, the cortex and pith ~ together being classed as ground tissue.

peristelar tissue; p.1.

The typical structure of the vascular cylinder of the adult primary stem in the Gyrnnosperms and Dicotyledons is, like that of the higher ferns, a hollow cylinder of vas- Structure of cular tissue enclosing a central parenchymatous pith.

The vascular tissue is typically separable into distinct collateral bundles (figs.

13, 23), the xylem of which is usually wedgeshaped in cross-section with the protoxylem elements at the inner extremity, while the phloem forms a band on the outer side of the xylem, and separated from it by a band of conjunctive tissue (mesodesm).

When the pith is large celled, the xylems of the bundles are separated from it by a distinct layer of conjunctive tissue called the endocycle, and a similar layer, the pericycle, separates the phloem from the cortex.

The pericycle, medullary rays, endocycle and mesoderm all form parts of one tissue system, the external conjunctive, and are only topographically separable.

The external conjunctive is usually a living comparatively small-celled tissue, whose cells are consider ably elongated in the direction of the stem-axis and frequently contain abundant starch.

Each J~ 1 1 / Stelein bundle has its own ~ investment of tissue P corresponding with external conjunctive, and now called peridesm.

In some astelic L- ~ stems (Nymphaeaceae) the number of bundles is greatly increased and they are scattered throughout the ground tissue.

Annuiar vessel, superficially obvious order through & I,~iterceiiuIar canal, the conjunctive tissue of the stele, 1.

In other cases the reduction goes much further, till the endodermis eventually comes to surround nothing but an intercellular channel formed in place of the stelar tissue.

In certain families of Angiosperms a peculiar tissue, called laticiferous tissue is met with.

They possess a delicate Laticiferous layer of protoplasm, with numerous small nuclei lining Tissue the walls, while the interior of the tube (corresponding with the cell-vacuole) contains a fluid called latex, consisting of an emulsion of fine granules and drops of very various substances suspended in a watery medium in which various other substances (salts, sugars, rubber-producers, tannins, alkaloids and various enzymes) are dissolved.

The relation ~ of the laticiferous tissue to the assimi I lating cells under which they often end, and the fact that where this tissue is / richly developed the conducting paren ~ chyma of the bundles, and sometimes also 4 the sieve-tubes, are poorly developed, as well as various other facts, point to the conclusion that the laticiferous system has an important function in conducting plastic substances, in addition to acting as an excretory reservoir.

- Laticiferous tissue is of two kinds:

The epidermis in the stair and the surface layer of the root soon becomes differentiated froit the underlying tissue.

In this case also the differentiation of leaf-bundles, which typically begins at the base of the leaf and extends upwards into the leaf and downwards into the stem, is the first phenomenon in the development of vascular tissue, and is seen at a higher level than the formation of a stele.

In this tissue fresh bundles may become differentiated, and what remains of it becomes the rays of the fully-formed stele.

The young tissue of the stelar cylinder, in the case of the modified siphonostele characteristic of the dicotyledonous stem, differs from the adjoining pith and cortex in its narrow elongated cells, a difference produced by the stopping of transverse and the increased frequency of longitudinal divisions.

The protoxylem and protophloem are developed a few cells from the inner and outer margins respectively of the desmogen strand, the desmogenic tissue left over giving rise to the segments of endocycle and pericycle capping the bundle.

Sometimes development stops altogether, and a layer of undifferentiated parenchyma (the mesodesm) is left between them; or it may continue indefinitely, the central cells keeping pace by their tangential division with the differentiation of tissue on each side.

In this case the formation of the primary bundle passes straight over into the formation of secondary tissue by a cumbium, and no line can be drawn between the two processes.

In the very frequent cases where the bundles have considerable individuality, the fibrous pericyclic cap very clearly has a common origin from the same strand of tissue as the vascular elements themselves.

In such cases it is part of the peridesm or sheath of elongated narrowcelled tissue surrounding the individual bundle.

New tangential walls arise in the cells which are the seat of cambial activity, and an initial layer of cells is established which cuts off tissue mother-cells on the inside and outside, alternately contributing to the xylem and to the phloem.

A tissue mother-cell of the xylem may, in the most advanced types of Dicotyledons, give rise to(I) a tracheid; (2) a segment of a vessel; (3) a xylem-fibre; or (4) a vertical file of xylem-parenchyma cells.

A tissue mother-cell of the phloem may give rise to (i) a segment of a sieve-tube with its companion cell or cells; (2) a phloem fibre; (3) a single phloem-parenchyma (cambiform) cell, or a ve~rtical file of short parenchyma cells.

It is essentially a living tissue, and serves to place all the living cells of the secondary vascular tissues in communication.

This type is found in nearly all Pteridophytes and, so far as is known, in Cycadofihices, both in primary and secondary tissue.

in the primary and secondary tissue, is that the proteid cells of the phloem are here always sister-cells of the leptoids and are known as companion-cells.

The main feature is the development of special vascular stereom and storage tissue.

In some cases special secreting tissues, resin ducts, oil glands, laticiferous tissue, crystal sacs, &c., may be developed among the ordinary secondary vascular elements.

When the vascular tissue of such plants is arranged Camblum in separate bundles these are said to be closed.

In stems with open bundles the formation of cambium and secondary tissue may be confined to these, when it is sard to be entirely fascicular.

In that case either very little secondary tissue is formed, as in the gourds, some Ranunculaceae, &c., or a considerable amount may be produced (clematis, barberry, ivy).

The interfascicular cambium may form nothing but parenchymatous tissue, producing merely continuations of the primary rays.

In other cases a most intricate arrangement of secondary tissue masses is produced, quite impossible to interpret unless all stages of their development have been followed.

The cambium in the root, which is found generally in those plants which possess a cambium in the stem, always begins in the conjunctive tissue internal to the primary phloems, and Camblum forms new (secondary) phloem in contact with the In Roots primary, and secondary xylem internally.

Thus the structure of an old thickened root approximates to that of an old thickened stem, and so far as the vascular tissue is concerned can often only be distinguished from the latter by the position and orientation of the primary xylems. The cambium of the primary root, together with the tissues which it forms, is always directly continuous with that of the primary stem, just in the same way as the tissues of the primary stele.

the cambium, and producing like the latter an external ~i, and an internal secondary tissue.

and the whole of the tissue it gives rise to is known as periderm.

The phellogen derives its name from the fact that its external product is the characteristic tissue known as cork.

The internal tissue formed by the phellogen is known as phelloderm, and consists usually of ordinary parenchyma.

In the former case the formation of phelloderm is trivial in amount; in the latter, considerable, since this tissue has to replace the cast-off cortex, as a metabolic and particularly a storage tissue.

supplementary vascular bundles, anomalous cambial zones, &c. It is often enormously developed and forms a very important tissue in roots.

In other cases, a similar formation of spongy but dead periderm tissue may occur for the same purpose in special patches, called pneumatodes, on the roots of certain trees living in marshy places, which rise above the soil in order to obtain air.

numerous, mainly German, workers, though no fundamentally new types of tissue have been discovered.

Fuchs and its allies, which form conspicuous members of the larger Algae, have their external cells much smaller, more closely put together, and generally much denser than the rest of their tissue.

They often cause a considerable hypertrophy of the tissue.

The swellings have been found to be due to a curious hypertrophy of the tissue of the part, the cells being filled with an immense number of minute bacterium-like organisms of V, X or Y shape.

After making its way into the interior, the intruder sets up a considerable hyper trophy of the tissue, causing the formation of a tubercle, which soon shows a certain differentiation, branches of the vascular bundles of the root being supplied to it.

The root is continually growing and so the sensitive part is continually changing its composition, cells being formed, growing and becoming permanent tissue.

The active contraction of muscular tissue has no counterpart in the plant.

But the case is obviously different where a plant dies because some essential organ or tissue tract has been destroyed, and other parts have suffered because supplies are cut offe.g.

In a large number of cases, however, the disease is purely local, and does not itself extend far into the organ or tissue affected.

Sclerophyllous leaves are ually characterized by entire or sub-entire margins, a thick cuticle, riall but rarely sunken stomata, a we1l-developed and close-set ilisade tissue and a feeble system of air-spaces.

Strengthening tissue of all kinds (and sometimes even the phloem) is more or less rudimentary.

Switch plants, such as Retama Retam and broom (Cytisus scoparius), have reduced leaves and some assimilating tissue in their stems; and stomata occur in grooves on the stem.

In such leaves, there are a well-marked cuticle, a thick epidermis, a thick hypodermis at least on the upper side of the leaf, well-developed palisade tissue, and a poorly developed system of air-spaces.

their leaves and, to some extent, their stems have much water-storing tissue and few intercellular spaces.

Strengthening tissue is feebly developed.

Laticiferous Tissue.The laticiferous tissue consists of a network of branching or anastomosing tubes which contain a coagulable fluid known as latex.

There are two types of tissue: non-articulate and articulate.

(1882); On the Laticiferous Tissue of Man-rhot Glazsovii (the Ceark Rubber), Quart.

The arrangement of the conducting tissue in the stem is characteristic; a transverse section of the very young stem shows a nunber of distinct conducting strands - vascular bundles - arranged in a ring round the pith; these soon become united to form a closed ring of bast and wood, separated by a layer of formative tissue (cambium).

They derive this moisture from the air by means of aerial roots, developed from the stem and bearing an outer spongy structure, or velamen, consisting of empty cells kept open by spiral thickenings in the wall; this sponge-like tissue absorbs dew and rain and condenses the moisture of the air and passes it on to the internal tissues.

The epidermis contains numerous groups of sense cells; beneath the epidermis there is rarely (Kynotus) an extensive connective tissue dermis.

The network is partly formed out of pigmented cells which are excavated and join to form tubes, the socalled botryoidal tissue, not found among the Rhynchobdellidae at all.

The main distinction is the occurrence in the tissue of the fruit, or beneath the rind, of clusters of cells filled with hard woody deposit in the case of the pear, constituting the "grit," while in the apple no such formation of woody cells takes place.

The foot of the limpet is a nearly circular disk of muscular tissue; in front, projecting from and raised above it, are the head and neck (figs.

On the whole the ganglia are strongly individualized in the Pectinibranchia, nerve-cell tissue being concentrated in the ganglia and absent from the cords.

The vascular system is not extensive, the arteries soon ending in the well-marked spongy tissue which builds up the muscular foot, parapodia, and dorsal body-wall.

Adult without shell; a sub-epithelial pseudoconch formed by connective tissue; pallial cavity ventral.

This cavity contains an irregular mass of whitish tissue, the fat-body, consisting of fat-cells which undergo degradation and become more or less filled with urates.

It was found that the tissues were attacked by phagocytic cells that became enlarged and carried away fragments of the tissue; the cells were subsequently identified as leucocytes or blood-cells.

These do not take a direct part in the formation of the new tissue, but it is believed merely yield their surplus acquisitions, becoming ordinary blood-cells or disappearing altogether.

Examination showed that although the weevil attacked the young buds these did not drop off, but that a special growth of tissue inside the bud frequently killed the grub.

Also, inside the young bolls which had been pierced a similar poliferation or growth of the tissue was set up, which enveloped and killed the pest.

It then often retains its vitality for a long time, apparently crawling as if it were itself a worm, a phenomenon which is at least partially explained by the extraordinary development of nervous tissue, equally distributed all through the walls of the proboscis, and either united into numerous longitudinal nerve-stems (Drepanophorus, Amphiporus) or spread out into a uniform and comparatively thick layer (Cerebratulus, sp.).

Superiorly the sheath either closely adheres to the muscular bodywall, with which it may even be partly interwoven, or it hangs freely in the connective tissue which fills the space between the intestine and the muscular body-wall.

In Carinella, Cephalothrix, Polia and the Metanemertines the two tegumentary layers with their different glandular elements are fused into one; a thick layer of connective tissue is situated beneath them (instead of between them) and keeps the entire cutaneous system more definitely separate from the muscular (fi g s.

c, Cellular tissue of the integument; Bm, basement membrane; cire.

I, outer circular, and long., longitudinal layer of muscular tissue; circ. 2, long.

The connective tissue of the integument and basement membrane imperceptibly merges into that which surrounds the muscular bundles as they are united into denser and definite layers, and this is especially marked in those forms (Akrostomum) where the density of the muscular body-wall has considerably diminished, and the connective tissue has thus become much more prominent.

It can then at the same time be observed, too, that the compact mass of connective tissue (" reticulum," Barrois) which lies between the muscular bodywall and the intestine is directly continuous with that in which the muscular layers are embedded.

The omnipresence of this connective tissue tends to exclude the formation of any perivisceral body cavity in Nemertines.

In Polia the connective tissue enclosed in the external muscular layer is eminently vacuolar - all the intermediate stages between such cells in which the vacuole predominates and the nucleus is peripheral and those in which the granular protoplasm still entirely fills them being moreover present.

To it belong (a) superficial grooves or deeper slits situated on the integument near the tip of the head, (b) nerve lobes in immediate connexion with the nervous tissue of the brain, and (c) ciliated ducts penetrating into the latter and communicating with the former.

These posterior brain-lobes, which in all Heteronemertines are in direct continuity of tissue with the upper pair of principal lobes, cease to have this intimate connexion in the Metanemertini; and, although still constituted of (I) a ciliated duct, opening out externally, (2) nervous tissue surrounding it, and (3) histological elements distinctly different from the nervous, and most probably directly derived from the oesophageal outgrowths, they are nevertheless here no longer constantly situated behind the upper brain-lobes and directly connected with them, but are found sometimes behind, sometimes beside and sometimes before the brain-lobes.

Here the pits split into two, one part ending in a sac lined with sensory epithelium, and embedded in nervous tissue, the other projecting backwards as a long, glandular, blind canal.

For the Heteronemertines arguments have been adduced to prove that here they have the physiological significance of a special respiratory apparatus for the central nervous tissue, which in all these forms is strongly charged with haemoglobin.

Anteriorly it finally communicates with the lacunae just mentioned, which surround the oesophagus, bathe the posterior lobes of the brain, pass through the nerve ring together with the proboscidian sheath, and are generally continued in front of the brain as a lacunar space in the muscular tissue, one on each side.

CT, Connective tissue.

cuticular tissue.

sub-cuticular tissue of the f, One of the retractors of the trunk and that of the pro g, A lemniscus.

Elastin occurs either as thick strands or as membranes; it constitutes the " elastic tissue " of the anatomist.

Latex, though chiefly secreted in vessels or small sacs which reside in the cortical tissue between the outer bark and the wood is also found in the leaves and sometimes in the roots or bulbs.

22) shows that it consists of a stout base, composed of a very hyaline connective tissue not uncommon in the tissues of the Brachiopoda, which is traversed by certain canals whose nature is considered below under the section (The Body Cavity) devoted to the coelom.

In Discinisca and Lingula there is further a lip-sinus or hollow system of channels which traverses the supporting tissue of the edge of the mantle and contains muscle-fibres.

The plexus of nerve-fibrils which underlie the ectoderm and are in places gathered up into nerves, and the great development of connective tissue, are worthy of notice.

Much of the latter takes the form of hyaline supporting tissue, embedded in which are scattered cells and fibres.

The lophophore and stalk are largely composed of this tissue.

Accordingly the diplostichous ommatoeum or soft tissue of the Arachnid's central eye should strictly be called " triplostichous," since the deep layer is itself doubled or folded.

The coils and branches of the tube are packed by connective tissue and blood spaces.

The entosternite was probably in origin part of the fibrous connective tissue lying close to the integument of the sternal surface - giving attachment to muscles corresponding more or less to those at present attached to it.

h, Epidermic cell-layer; mes, mesoblastic connective tissue; n, nerves; II, III, IV, V, depressions of the epidermis in each of which a cuticular lens will be formed.

- Section through a portion of the lateral eye of Limulus, showing three ommatidia - A, B and C. hyp, The epidermic cell-layer (so-called hypodermis), the cells of which increase in volume below each lens, 1, and become nerve-end cells or retinula-cells, rt; in A, the letters rh point to a rhabdomere secreted by the cell rt; c, the peculiar central spherical cell; n, nerve fibres; mes, mesoblastic skeletal tissue; ch, chitinous cuticle.

tiss, Connective tissue (mesomediately underlying the lens.

An internal skeletal plate, the so-called " entosternite " of fibrocartilaginous tissue, to which many muscles are attached, is placed between the nerve-cords and the alimentary tract in the prosoma of the larger forms (Limulus, Scorpio, Mygale).

5), Dracaena and Cordyline include arborescent species in which the stem increases in thickness continually by a centrifugal formation of new tissue; an extreme case is afforded by Dracaena Draco, the dragon-tree of Teneriffe.

The caseous necrosis of the implicated mass of lung tissue, and indeed of tubercles generally, is held to be, in great measure, the result of the necrotic influence of the secretions from the bacillus.

Disease we may define, accordingly, as any departure from the normal standard of structure or function of a tissue or organ.

- When the blood supply is entirely cut off from a tissue the tissue dies, and in the act of dying, or afterwards, it suffers certain alterations dependent upon its surroundings.

II.); that is to say, it dies and falls a prey to the organisms which excite putrefaction, just as would happen to any other dead animal tissue were it unconnected with the body.

Muscle and white fibrous tissue follow next in order, while elastic tissue and bone are the last to show signs of disintegration.

The temperature at which the limb is kept, no doubt, favours and hastens the natural process of destruction, so that putrefaction shows itself sooner than would be the case with a dead tissue removed from the body and kept at a lower temperature.

Nevertheless, gangrene is nothing more or less than the putrefactive fermentation of an animal tissue still attached to the body.

If the amount of liquid contained in the tissue be small in quantity the part mummifies, giving rise to what is known as " dry gangrene."

Should the portion of tissue deprived of its circulation be contained in an internal organ, as is so often the case where the obstruction in the artery is due to embolism, it becomes converted into what is known as an " infarction."

If absorption be not complete the mass undergoes caseation and becomes surrounded by a capsule of fibrous tissue - being sharply cut off from the healthy tissue.

If, on the other hand, any pathogenic organisms be present the results are disastrous because the tissue, deprived of its nervous trophic supply, has greatly lessened resistance.

It is much more likely, as Verworn alleges, that the nerves which influence the characteristic function of any tissue regulate thereby the metabolism of the cells in question - in other words, that every nerve serves as a trophic nerve for the tissues it supplies.

The effect of overwork upon an organ or tissue varies in accordance with (a) the particular organ or tissue concerned, (b) the amount of nourishment conveyed to it, and (c) the power of assimilation possessed by its cells.

The term hypertrophy is used when the individual tissue elements become bigger to meet the demands of greater functional activity; hyperplasia, if there is an increase in the number of these elements; and pseudo-hypertrophy, when the specific tissue element is largely replaced by another tissue.

Should there be much loss of tissue of an organ, the cells of the remaining part will enlarge and undergo an active proliferation (hyperplasia) so that it may be made up to the original amount.

Increased work thrown on to a tissue may produce hypertrophy, but, if this excessive function be kept up, atrophy will follow; even the blacksmith's arm breaks down owing to the hypertrophic muscle fibres becoming markedly atrophied.

Injury and loss of tissue are usually followed by repair, and both the destructive and reparative changes are, as a rule, classified under the term inflammation.

If the abscess be deeply situated in some tissue and not able to open on to a free surface so allowing the contents to be drained off, the phagocytic cells play a very prominent part in the resolution of the abscess.

Then they develop .definite fibrils which differentiate into fibrous laminae forming a zone which shuts off the abscess from the healthy tissue and so prevents the further invasion and injurious effects of the microorganism.

IV.), that of " sclerosis " is used when such a deposition of fibrous tissue occurs within the central nervous system.

Tumours Or New Growths The various definitions of the term " new growth " leave us with a definite conception of it as a new formation of tissue which appears to originate and to grow independently.

According to the hypothesis of Waldeyer and Thiersch there is perfect equilibrium between the normal epithelium and its supporting structure, the connective tissue, but with advancing age this balance is upset owing to the connective tissue gradually losing its restraining power.

The separated cells become intermingled with other tissue elements amongst which they lie dormant with their inherent power of proliferation in abeyance.

He holds that new growths arise, both before birth or at any subsequent period of life, by the separation of cells or clumps of cells from their normal position, and that in health there is a balance between the various tissues and tissue elements regulated by what he calls the " tissue-tension " of the part, i.e.

Then we have Beard's " germ-cell " hypothesis, in which he holds that many of the germ-cells in the growing embryo fail to reach their proper position - the generative areas - and settle down and become quiescent in some somatic tissue of the embryo.

They are direct lineal descendants of the cells introduced, and are in no way formed from the tissue cells of the host in which they are placed and grow.

Not only is this true of epithelial cells, but - the connective tissuecells of the supporting structure of cancerous growth, after repeated transplantation, may become so altered that a gradual evolution of apparently normal connective tissue into sarcomatous elements takes place, these giving rise to " mixed tumours."

The fact that it is possible to propagate these cells of one animal for years in other animals of the same species, without any loss of their vegetative vitality, suggests that this continued growth is kept up by a growth-stimulating substance present in the proper species of animal; this substance, however, has not the power of transforming the normal tissue into a cancerous one.

- Symmetrical gangrene of toes (3 months' duration), showing the sharp " line rof demarcation " between the mummified toes and the more healthy tissue.

i iuroblasts in young temporary granulation tissue.

- Scar tissue in a healed wound.

lobular cirrhosis, of ` Gin-drink, I's Li, showing well-formed fibrous overgrowth which has divided up the liver tissue into irregular masses and caused atrophic and d egenerative changes in the liver cells.

- Healing abscess showing a wall of young cellular and vascular granulation tissue, which separates the pus area (top of Fig.) from the muscle fibres seen at lower part of Fig.

- Chronic interstitial myocarditis, showing the muscle fibres in the heart wall being separated and becoming atrophied by a slow fibrous overgrowth of the connective tissue.

- Granulauun tissue showing the character and relation of the cellular elements to the new blood-vessels in the young temporary tissue.

It may merely act locally in some way, and so render that part susceptible to unknown tissue stimuli which impart to the cells that extraordinary power of proliferation characteristic of new growth.

A defect in co-ordination allows the stimulated active vegetative cellular elements, or the more fully differentiated tissue, to over-develop and so form tumours, simple or malignant.

Other Tissue Products Mucoid.

The connective tissue is supplied normally with a certain amount of these mucinoid substances, no doubt acting as a lubricant.

In the wasting of the thyroid gland in myxoedema, or when the gland is completely removed by operation, myxomatous areas are found in the subcutaneous tissue of the skin, nerve-sheaths, &c.

In acute and chronic alcoholism, in phthisis, and in other diseases this fatty condition may be very extreme, and is commonly found in association with other tissue changes, so that probably we should look on these changes as a degeneration.

Adiposity or obesity occurs when we have an excessive amount of fat stored in the normal connective-tissue areas of adipose tissue.

Note the sharp line of demarcation between the growth and the tissue in which it is growing.

A simple tumour composed of well-differentiated fibrous tissue.

The fibres are arranged in irregular bundles forming a dense firm tissue.

These are pressed upon and become atrophied, and may ultimately be replaced by adipose tissue.

These soluble salts combine with the albumins in the body, and are deposited as minute granules of silver albuminate in the connective tissue of the skin papillae, serous membranes, the intima of arteries and the kidney.

It also occurs in bones and elastic tissue, but is not present in the normal human liver.

drill-bones) may develop in a soft tissue with no natural bone-forming tendencies, as a result of interrupted pressure, or a fatty tumour may arise in the midst of the natural subcutaneous fat in the same circumstances.

It is invariably the result of some cause acting generally, such as renal disease, valvular defect of the heart, or an impoverished state of the blood; while a mere oedema is usually dependent upon some local obstruction to the return of blood or lymph, or of both, the presence of parasites within the tissue, such as the filaria sanguinis hominis or trichina spiralis, or the poisonous bites of insects.

In a given case of anasarca due to a cause acting generally, it will be found that the liquid of the pleural cavity always contains the highest percentage of proteid, that of the peritoneal cavity comes next, that of the cerebral ventricles follows this, and the liquid of the subcutaneous areolar tissue contains the lowest.

It may be asked, however, whether a dropsical tissue is being held in a high state of nutrition, and whether, on the contrary, the presence of lymph in excess in its interstices does not tend to impair its vitality rather than to lend it support.

Bainbridge suggests that a retention of metabolic products may cause the oedema in renal disease, Bradford having previously shown that loss of a certain amount of renal tissue caused retention of metabolic products in the tissues.

As sodium chloride is one of the most permeable of crystalloids it seems strange that damage to the renal tissue should impede its excretion.

i.; Afanassieff, " Granulation Tissue and Infection," Centralbl.