OF THE CAPILLARY VESSELS. 263 



of a change of direction or a bending of a minute artery, which 

 becomes a venous radicle; at others a capillary artery and 

 vein parallel to each other, also exchange communicating radi- 

 cles, at the point where the artery changes into a vein; again, 

 and frequently, several capillary arteries terminate or are con- 

 tinued into a single capillary vein. In all cases the commu- 

 nicatiqn occurs in vessels of the capacity of from one to four 

 or five coloured globules. 



330. Modern physiologists have recently raised doubts 

 respecting the direct communication of the arteries and veins. 

 Doellinger thinks that the arteries, at their extremity, cease 

 to have any parietes, and that the blood flows uncontined in 

 the solid substance of the body, which he calls mucous; that 

 at this point, one part of the blood is converted into mucous 

 substance, and that another part of it continues its course 

 joined to sanguified mucous substance, which is set in motion 

 in liquid mass, and penetrates into the venous and lymphatic 

 vessels, arising from the mucous substance as the arteries ter- 

 minate in it. 



Wilbrand goes still farther, and admits a still more com- 

 plete metamorphosis in the circulation; according to him the 

 whole of the blood is converted into organs, or into mucous 

 substance and into secreted fluids, and the organs becoming 

 fluid in the same degree, is converted again into venous fluid 

 and lymph, which continue the circulation, and also become 

 the matter of excretions. 



According to one of these opinions, a part, and according 

 to the other, the whole of the blood becomes solid, and like- 

 wise a part or the whole of the organs is rendered fluid at 

 each round of the circulation. In the one as in the other, the 

 solid mass of the body is interposed between the terminations 

 of the arteries and the origin of the veins and lymphatics. They 

 both suppose that the microscopical inspection of living ani- 

 mals and injections are deceitful means of determining the 

 communication between the arteries and veins. 



391. The direct continuity of the arteries and lymphatics 

 is not so well demonstrated as that of the veins and arteries. 

 Many anatomists, however, have admitted, with Bartholin, 

 35 



