170 KANSAS UNIVERSITY QUARTERLY. 



adreno-lumbalis, the right renal and adrenal, left renal and 

 postcava, and the lumbar azygos and adrenal. (See plate 

 XXXVI, b, m.) 



The adreno-lumbalis of the right side emptied into the post- 

 cava one centimeter above the ligature. It was very large, as 

 was also the ileo-lumbalis, which sent numerous tributaries to 

 the lateral abdominal wall and psoas muscles, some of its 

 branches opening into the postcava below the ligature, others 

 into the iliac and ascending vessel that gave rise to the azygos. 



On the left side several large branches arose from the adreno- 

 lumbalis, which connected on this side with the renal vein. 

 The largest of its branches extended anteriorly along the side 

 of the wall, to empty into the azygos near the first lumbar. 

 Another vessel that emptied here was distributed in the dia- 

 phragm, wdiile others that are found in the lateral wall con- 

 nected w^itli the postcava above the ligature. 



Near the heart the azygos was about four- fifths the size of 

 the postcava, while in the normal cat it is from one-half to 

 two-thirds the size. The four lumbar and superior intercostals 

 were larger than normal. 



From a study of the changes instituted by the ligation of the 

 postcava, there seems to be a tendency to establish connections 

 between the two parts of the cava separated by the ligature. 

 This is seen in the development of the numerous tortuous 

 anastomosing vessels between the separated parts as well as be- 

 tween branches of vessels that empty into them. It requires 

 further study to determine whether these vessels developed 

 from capillaries into veins, or arose as new tributaries from ex- 

 isting veins. 



It is seen, moreover, that the tendency is to return the blood 

 to the heart through the most direct path of least resistance. 

 The blood entering the postcava below the ligature passes 

 through the lumbar veins into the spinal sinuses and origin of 

 the azygos vein, or directly, from the postcava through the 

 lumbar veins to the azygos. Then, too, the paths conveying 

 blood from other abdominal regions to the thoracic azygos we 

 saw were strengthened. It is evident that the azygos has 

 risen in importance, receiving now from all possible directions 

 most of the blood that is to be returned to the heart from re- 

 gions below the ligature. 



