A survey of the vegetable kingdom indicates that evolution has proceeded, on the whole, from the simple to the complex; at the same time, as has been already mentioned, evidence of reduction or degeneration in common.
Despite all this, one must not fall into the easy error of exaggerating the degeneration into which the Jewries of the world fell from the middle of the 17th till the middle of the 18th century.
The variety of special developments of structure accompanying the atrophy of typical organs in the Opisthobranchia and general degeneration of organization is very great.
So, too, degeneration is not to be lightly assumed as the explanation of a simplicity of structure.
There is a very definite criterion of the simplicity due to degeneration, which can in most cases be applied.
Spencer), as in the Araneae and Opiliones, and, on the other hand, may terminate in simplification and degeneration, as in the Acari.
The reduction of the organism to seven leg-bearing somites, of which the first pair, as in so many Eu-arachnida, are chelate, is a form of degeneration connected with a peculiar quasi-parasitic habit resembling that of the crustacean Laemodipoda.
Idem, " Degeneration, a Chapter in Darwinism," 1878, reprinted in the Advancement of Science (Macmillan, 1890); 20.
Claus, " Degeneration of the Acari and Classification of Arthropoda," Anzeiger d.
Another important factor in the present condition of zoological knowledge as represented by classification is the doctrine of degeneration propounded by Anton Dohrn.
It is Dohrn's merit to have pointed out 1 that this assumption is not warranted, and that degeneration or progressive simplification of structure may have, and in many lines certainly has, taken place, as well as progressive elaboration and in other cases continuous maintenance of the status quo.
The general purpose is to give something like an equivalence of importance to divisions or branches indicated by the same term, but it is not intended to imply that every phylum has the Ursprung der Wirbelthiere (Leipzig, 1875); and Lankester, Degeneration (London, 1880),, ti, ae / .r ?
A knowledge of the bacteriology of scrofulous affections of bone and joints, such as caries and gelatinous degeneration, has shown that they also are tubercular diseases - that is to say, diseases due to the presence locally of the tubercle bacillus.
The deleterious influence of high bloodpressure has engaged the attention of physicians and pathologists in later years, and the conclusion arrived at is, that although it may arise from accidental causes, such as malcomposition of the blood, yet that in many instances it is a hereditary or family defect, and is bound up with the tendency to gout and cirrhotic degeneration of the kidney.
The muscles suffer at an early period: they fall off in bulk, and later suffer from fatty degeneration, the heart being probably the first muscle to give way.
A salivary gland degenerates when its nerve-supply is cut off.
When a nerve-trunk is separated from its central connexion, the distal portion falls into a state of fatty degeneration (Wallerian or secondary degeneration).
The toxic actions produced in continued fevers, in certain chronic diseases, and by intestinal parasites largely aid in producing degeneration, emaciation and atrophy.
Thus workers in lead suffer from the effects of this substance as a poison, those who work in phosphorus are liable to necrosis of bone and fatty degeneration of the blood vessels and organs, and the many occupations in which dust is inhaled (coalmining, stone-dressing, steel-polishing, &c.; fig.
Cell in a state of degeneration and chromatolysis; the large rounded body in the cell is a cancer parasite.
- Fatty degeneration of heart from case of perni cious anaemia.
- Fatty degeneration of kidney from case of starvation.
This term is usually applied to a semi-solid substance of homogeneous and gelatinous consistence, which results partly from excretion and partly from degeneration of cellular structures, more particularly of the epithelial type.
Serous degeneration is met with in epithelial cells in inflammatory conditions and following on burns.
Fatty degeneration is a retrogressive change associated with the deposit of fatty granules or globules in the cytoplasm, and is caused by disorganized cellular activity (figs.
Over and above the bacterial intoxications we have a very extreme degree of fatty degeneration, widely distributed throughout the tissues, which is produced by certain organic and inorganic poisons; it is seen especially in phosphorus and chloroform poisoning.
Fatty degeneration is common to all dead or decaying tissues in the body, and may be followed by calcification.
Autolysis is a disintegration of dead tissues brought about by the action of their own ferments, while degeneration takes place in the still living cell.
From whatever cause the tissues become disorganized and undergo fatty degeneration, the fatty acids may become liberated and combine with the alkalies to form potash and soda soaps.
The fibrils of the outer coat also show the change to a less extent, while the degeneration very rarely spreads to the middle coat.
Hyaline degeneration is found in certain acute infective conditions; the toxins specially act on these connective-tissue cell elements.
They are probably a degeneration-product of cells.
611; Pelagatti, " Blastomycetes and Hyaline degeneration," Arch.
Waller (1816-1870), who tracked the line of nervous strands by experimental sections, and showed that when particular strands are cut off from their nutritive centres the consequent degeneration follows the line of the separated strands.
In such cases the paths of degeneration are so neatly defined that, when the tissues are prepared after death by modern methods, they are plainly to be seen running along certain columns, the subdivisions of which in the normal state may hardly be distinguishable one from another: some run in strips along the periphery of the spinal cord, at its anterior, middle or posterior segments, as the case may be; in other cases such strips occur within its substance, whether along columns of cells or of white matter.
With changes of the pressures of the blood in arteries, veins or capillaries, and in the heart itself and its respective chambers, static changes are apt to follow in these parts; such as degeneration of the coats of the arteries, due either to the silent tooth of time, to persistent high blood pressures, or to the action of poisons such as lead or syphilis.
Marey, 1863) attention was drawn to the physical features of the circulation, to the signs of degeneration of the arterial tree, and less definitely to the fluctuations of blood pressure; but as we have said under the consideration of diseases of the heart, the kymographs of Ludwig and his pupils brought out these fluctuations far more accurately and completely.
Their structure has undergone little degeneration in connexion with this habit, and may be compared organ for organ with that of the Planarians.
The only organs that exhibit any sign of degeneration are those of sense, but in the ectoparasitic Trematodes simple eye-like structures are present and perhaps serve as organs of temperature.
On the degeneration of the polypide, its nutritive material is apparently absorbed for the benefit of the zooid, while the pig mented substances assume a spheroidal form, which either remains as an inert "brown body" in the body-cavity or is discharged to the exterior by the alimentary canal of the new polypide.
His universal process of Evolution seems to give Spencer a criterion of" higher "and" lower " progression "and" degeneration,"independent of the accidents of actual history, and unattainable by strictly Darwinian methods.
He recognized the fact that the shells of molluscs, which grow by successive additions, preserve unchanged the whole series of stages of their individual development, so that each shell of a Cretaceous ammonite, for example, represents five stages of progressive modification as follows: the first is the periode embryonnaire, during which the shell is smooth; the second and third represent periods of elaboration and ornamentation; the fourth is a period of initial degeneration; the fifth and last a period of degeneration when ornamentation becomes obsolete and the exterior smooth again, as in the young.
The essential part of the medicinal treatment of this condition is the administration of iodides, which are able to decompose the insoluble albuminates of lead which have become locked up in the tissues, rapidly causing their degeneration, and to cause the excretion of the poisonous metal by means of the intestine and the kidneys.
The history of the male communities is to a certain extent parallel with the female, but they were never so numerous and their degeneration was far more rapid.
The drug is contra-indicated in all cases where the heart is already beating too slowly; in aortic incompetence - where the prolongation of diastole increases the amount of the blood that regurgitates through the incompetent valve; in chronic Bright's disease and in fatty degeneration of the heart - since nothing can cause fat to become contractile.