The dorsal vessel also communicates with the ventral vessel indirectly by the intestinal sinus, which gives off branches to both the longitudinal trunks, and by tegementary vessels and capillaries which supply the skin and the nephridia.
The capillaries sometimes (in many leeches and Oligochaeta) extend into the epidermis itself.
In favour of seeing in the lateral trunks and their branches a vascular system, is the contractility of the former, and the fact of the intrusion of the latter into the epidermis, matched among the Oligochaeta, where undoubted blood capillaries perforate the epidermis.
These tubes are lined by flattened epithelium and often contain blood capillaries; they communicate with the coelom and are to be regarded as prolongation of it into the thickness of the body wall.
The arterial system is very completely developed in both Limulus and Scorpio, branching repeatedly until minute arterioles are formed, not to be distinguished from true capillaries; FIG.
These cells of various shapes are seen in large numbers, mainly lying in a direction parallel to the new vessels and capillaries, which all run at right angles to the wound surface.
The swollen waxy capillaries are pressing on the columns of liver cells and are causing marked atrophy.
It spreads forwards, affecting the supporting fibres outside the epithelium of the capillaries, and then passes to the connective-tissue fibrils of the veins.
Certain free mobile cells within the body, such as blood-leucocytes, as well as others which are fixed, as for instance the endothelium of the hepatic capillaries, have the property of seizing upon some kinds of particulate matter brought within their reach.
Melanine particles formed in the spleen in malaria, which pass along with the blood through the liver, are appropriated by the endothelial cells of the hepatic capillaries, and are found embedded within their substance.
Thus Ludwig was of opinion that the lymph-flow is dependent upon two factors, first, difference in pressure of the blood in the capillaries and the liquid in the plasma spaces outside; and, secondly, chemical interchanges setting up osmotic currents through the vessel-walls.
Heidenhain recognizes two classes, first, such substances as peptone, leech extract and crayfish extract; and, secondly, crystalloids such as sugar, salt, &c. Starling sees no reason to believe that members of either class act otherwise than by increasing the pressure in the capillaries or by injuring the endothelial wall.
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.
Cuticle; b, basal membrane; c, outer circular muscles; d, epidermal cells depressed below the surface usually occupied by them in other animals; e, gland cell; f, " flamecell " (the reference line stops a little short); g, outer longitudinal muscles; h, a calcareous corpuscle; i, dorso-ventral muscles; j, a " parenchyma " cell (probably nervous); k, nerveplexus; 1, excretory vessel giving off capillaries ending in flamecells; m, a sense-cell; n, a muscle-cell; o, ending of the same; p, ending of sense-cell; q, opening of gland-cell; r, superficial cuticle.
Malpighi's demonstration of the blood capillaries in 1668, and six years later he gave the first accurate description of the red blood corpuscles, which he found to be circular in man but oval in frogs and fishes.
The parasites are frequently more numerous in the spleen, bone-marrow, kidneys, &c., than elsewhere, and it has been found that multiplication goes on rather more actively in the capillaries of these organs.
Death is due either to weakness and emaciation (in chronic cases), or to blocking of the cerebral capillaries by the parasites (where these are abundant), or to disorganization of the nervous system (paraplegic and sleepingsickness cases).
From these intralobular capillaries run toward the centre of the lobule, forming a network among the polygonal hepatic cells.
At a, a the capillaries of one lobule communicate with those adjacent to it.
It consists of arteries, veins and sinuses, but ramified capillaries are usually absent except in the integuments of Cephalopods.
One result of this among the Vertebrata is that the eyeball is pink in colour, since the cornea, iris and retina being transparent, the red blood contained in the capillaries is unmasked by the absence of pigmentary material.
This system is in no true sense a vascular system; there are no capillaries, and the fluid it contains, which is corpusculated, can hardly have a respiratory or nutritive function.
And although effects may some times be produced in a mechanical manner by bacteria plugging capillaries of important organs, e.g.
In the human subject, often due to streptococci, the process is similar, but the organisms are found especially in the capillaries of the internal organs and may not be detectable in the peripheral circulation during life.