THE ANTERIOR VENA CAVA. 615 



roots, massed in a very dense network, converge towards the superior 

 portions by diminishing in number and augmenting in volume, and terminate 

 in forming themselves, by the aid of successive anastomoses, into ten 

 or twelve principal branches which again unite into two considerable 

 vessels (Fig. 292, 6), situated at the superior limit of the plexus. These 

 vessels, finally, by their last fusion at the inferior extremity of the first 

 phalanx, constitute the digital vein, the satellite of the artery of the same 

 name (Fig. 292, 5). 



" Considered from below upwards, in a foot previously prepared by 

 injection, the digital vein, divided into two branches, subdivides itself 

 into secondary branches and ramuscules which diverge and spread over the 

 convex surface of the cartilage and coronary cushion, resembling somewhat 

 the disposition of trees trained on espaliers, whose spreading branches are 

 fixed to the walls on which they ramify. 



" The two peripheral branches of the superficial cartilaginous plexus 

 establish communications with the opposite cartilaginous plexus, in con- 

 tracting direct anastomoses with the branches of the plexus which arc 

 symmetrical to them. 



" The anterior anastomosing canals are double and superposed. 



" The most inferior and superficial is constituted by the large vein (Fig. 

 292, 3') thrown slantingly across from one plexus to the other in the median 

 plane, and on the external surface of the extensor tendon ; this receives a 

 considerable multitude of venous ramuscles, which emerge from the anterior 

 part of the podophyllous plexus. 



" This first communicating vein joins the anterior branches of the carti- 

 laginous plexus. 



" The second communicating vein, situated three-quarters of an inch above 

 the first, and beneath the tendon, is thrown transversely from one anterior 

 branch of the plexus to the other. They open into each other on each sido, 

 at the same point where the first communicating vein enters. 



" Sinuous in the whole of its track, sometimes double, and sometimes 

 formed of several confluent veins, as in Fig. 292, this anastomosing canal 

 serves as an outlet for several deep veins. 



" The anastomosis between the posterior peripheral branches of the 

 cartilaginous plexus is formed by an irregularly curved and long vein of 

 large calibre, sinuous or broken in its course, but always considerably 

 longer than the distance from the two cartilaginous plates between which it 

 is extended. 



" This posterior communicating vein acts as a confluent to the canals 

 emerging from the cartilaginous bulbs, and to the posterior part of the solar 

 plexus, which throws into it five or six well-developed afferent veins. 



"Deep cartilaginous layer or plexus. The deep layer of the carti- 

 laginous plexus is formed : 



"1. By somewhat large ascending branches from the posterior part of the 

 podophyllous and solar plexuses. 



" 2. By the deep internal venous apparatus of the third phalanx. 



"3. By the deep veins arising from the coronary bone and the liga- 

 ments and tendons surrounding it. 



" The ascending branches of the podophyllous tissue are introduced by 

 the numerous foramina which traverse the base of the cartilaginous plate 

 and the inferior fibrous covering of the plantar cushion ; they follow the canals 

 which continue those foramina in the substance of the cartilage, and reach 

 its internal face, along with the branches proceeding from the intra-osseous 



