210 



OP THE BLOOD AKD CIECULATION. 



axis of the vessel. The larger vessels admit several blood- 

 corpuscles together, and in the decidedly arterial or venous 

 branches they are observed passing on in all positions three, 

 four, and five abreast, over and near to one another, but those 

 in the centre of the current always in more rapid motion than 

 those on its outside and in contact with the walls of the 

 vessel. (Figs. 227 and 228.) Occasionally we observe single 

 vessels of larger calibre running very immediately under the 

 epithelium (a), which is made up of tubular cells with nuclei 

 (b, b, b, 5), through which the fibrous parietes of the vessel are 

 seen shining (fig. 22S). 



Fig. 227. Vascular rete and circulation of the web of the hind-foot of 

 Rana temporaria, magnified 110 times. The individual cells of the paren- 

 chyma are indefinite and obscure. The black spots, some of them star- 

 shaped, are depositions of pigmentary matter. The deep venous trunk, 

 a, composed of three principal branches, b, b, b, is covered with a rete of 

 smaller vessels. Mingled with the oval-shaped blood-globules, the smaller 

 and rounder lymph-globules are apparent; here, under the blood- globules, 

 there, more on the outside of the stream. 



