143^ 



the left side of the base of the heart from before backwards, and with 

 a shght obliquity downwards. On making a dissection of this vein, 

 it was found to be none other than a well marked example of a left 

 anterior vena cava, which, formed by the union of the left jugular 

 and subclavian veins, passed backwards in the direction just indicated. 

 Curving round the posterior border of the heart in the auriculo-ventri- 

 cular groove, it became continuous with the coronary sinus, and opened 

 into the posterior part of the right auricle. The common vein which 

 receives the left vertebral and superior intercostal veins, opened into 

 it a short distance behind its commencement. The internal mammary 

 vein joined it immediately after its formation by the union of the ju- 

 gular and subclavian veins. This was a slight variation from what is 

 found to be the average arrangement; for the mammary vein usually 

 opens into the anterior cava behind the point of entrance of the com- 

 mon affluent formed by the vertebral and superior intercostal veins. 



Left Anterior 



Right 

 Anterior Cava 



Posterior Aorta 

 Vena Azygos 



Pulmonary Artery 

 Pulmonary Veins 



Posterior 

 Vena Cava 



Fig. 1. Heart of Dog viewed from the left. 



Bearing in mind the fact that in those cases in which there are 

 two anterior (superior) Venae cavse in man, there is often a small trans- 

 verse vein (transverse jugular) connecting them, this was sought for. 

 Though the search was careful, and the veins were naturally injected 

 with blood — the dog having been destroyed by prussic acid — co- 

 agulated by the formalin which had been used, no transverse vein was 

 found. It was evident, therefore, that if any such vein had ever existed, 

 it had entirely disappeared. It seems more feasible to conclude, how- 

 ewer, that there had never been any such communication; and the 



