LYMPHATICO-VENOUS COMMUNICATIONS 449 



the fact that the postcava is developed on the right side of the 

 aorta, necessitates an increase in the length of the left renal vein. 

 The left suprarenal and sex veins open into the corresponding 

 renal; while those on the right side of the body enter the post- 

 cava direct, the suprarenal above, and the sex vein below the 

 renal vein. Two small phrenic veins from the pillars of the dia- 

 phragm usually enter the postcava directly caudad of the hepatic 

 tributaries. These veins may at times, however, enter the renal 

 or suprarenal veins. 



In one specimen of Cebus hypoleucus (plate 5) the normal 

 position of the veins was reversed, the postcava being situated 

 on the left side of the aorta. This was the only radical varia- 

 tion from the normal position of the postcava which was met 

 with in an examination of the venous system of a very large num- 

 ber of monkeys. It is interesting to note that in this individual 

 the morphological position of the veno-lymphatic communica- 

 tions was not changed, though these communications were of 

 course shifted to the opposite side of the postcava. This varia- 

 tion in the position of the postcava and the resultant shifting of 

 the lumbar lymphatic trunks, illustrates very beautifully the recip- 

 rocal relationship between the veins and the lymphatics. Hunt- 

 ington and McClure^ have pointed out the reason for this rela- 

 tionship between the veins and the lymphatics. This is very 

 clearly expressed by Dr. Huntington^ in a review of the above work. 

 *'The developmental shifting of the primitive redundant embry- 

 onal venous system from the original bilateral symmetrical type 

 to the dextro-venous condition of the adult favors the sinistral 

 development of the main lymphatic channels, which replaces 

 the atrophied left segment of the primitive bilateral symmetri- 

 cal venous system of earlier embryonal stages." Naturally in 

 this variation in the position of the postcava one would expect 

 to meet with a corresponding variation in the position of the 

 lymphatics. 



' George S. Huntington and C. F. W. McClure, The Development of the Main 

 Lymph Channels of the Cat in their Relations to the Venous System, Am. Jour, 

 of Anat., vol. 6, 1907. 



* George S. Huntington, The Genetic Interpretation of the Development of 

 the Mammalian Lymphatic System, Anat. Record, vol. 2, 1908. 



THE AMERICAN JOURNAL OP ANATOMY, VOL. 12, NO. 4 



