TEE ANTERIOR VENA CAVA. 699 



" To facilitate its description, we recognize in it three parts distinct by their 

 situation, though they only form a continuous one. They are : 



" 1 . The solar plexus. 



"2. ThB podophyllous plexus. 



" 3. The coronary plexus. 



" A Solar Plexus. — The veins of the solar plexus are remarkable for the 

 equaUty of their calibre throughout the whole extent of the plantar surface, and 

 by the almost absolute absence of anastomotic communications with the deep 

 parts. 



" Sustained in a special fibrous web {plantar reticulum), which replaces the 

 periosteum at the lower surface of the phalanx, and is a continuation of the 

 corium of the villous tissue, these veins appear indeed to have so little commu- 

 nication, except with each other, that it is possible to detach the plantar reticu- 

 lum from the superior face of the third phalanx without disturbing them. 



" The general disposition of the veins in the texture of the reticulum 

 supporting them, closely resembles that of the secondary ribs of the limb (or 

 laminar meritliaX) of certain asymmetrical leaves. In their course they follow an 

 irregularly broken Hne, intercepting each other by joining at short intervals, so 

 as to form unequal-sized, unsymmetric, polygonal spaces. 



" These veins discharge themselves by a double canal — a central, the least 

 considerable and least constant ; the other, peripheral or circumflex, correspond- 

 ing to the artery of the same name,^ and of which it is the satellite vein. 



" Central canal. — The central canal is formed by the simultaneous anasto- 

 moses of a crowd of venous ramifications converging towards the centre of the 

 digit. It is of a parabolic shape, and embraces in the concavity of its curvature 

 the point of the pyramidal body, whence it throws its two branches in a parallel 

 manner on the sides of that body, into the bottom of the lateral lacunas as far as 

 the cartilaginous bulbs, where it proceeds to the external coronary plexus. This 

 disposition is not constant, however, as specimens are frequently met with in 

 which this central canal is replaced by multiple veins, which are more consider- 

 able than those forming the whole of the plexus, and which serve them as over- 

 falls towards the superficial coronary plexus. 



" Circumflex or peripheral vein. — This vein is of large calibre, and formed by 

 divergent ramifications from the solar plexus, as well as the descending veins 

 of the podophyllous plexus ; it margins the external border of the villous tissue, 

 in following a slightly undulous hne within the circumflex artery, of which it is 

 the satellite. It is sometimes broken up, at certain points of its course, into 

 several smaller canals which are continuous with its trunks. 



" In its circular route, all the divergent solar and descending podophyllous 

 veins are discharged into it, and it terminates, at the extremities of the crescent 

 formed by the third phalanx, in several large branches which pass beneath the 

 podophyllous tissue to the lateral cartilage, where they concur to form the 

 superficial coronary plexus. 



"B. Podophyllous Venous Plexus or Network. — The veins of the 

 podophyllous plexus exhibits a disposition analogous to those of the solar plexus ; 

 like them, they are sustained in the meshes of a fibrous texture (the reticulum 

 processigerum of Bracy Clark, the suhpodophtjlJous reticulum of French Veteri- 

 narians) spread on the anterior surface of the bone, in the same way as the 

 periosteum is on other bones, and continuous with the corium of the laminal 

 ' The inferior circumflex artery of the foot. 



