632 MR. C. H. O'UONOGHUE ON THE 



The Right Efferent Renal Vein (Y. venalis revehens, Schlemm) 

 originates along the inner margin of the kidney at its posterior 

 end, runs to the anterior end, and after a short independent 

 course in front of the kidney unites with its fellow of the opposite 

 side to give rise to the post-caval vein. 



The Left Efferent Renal Vein also has its origin along the inner 

 margin of the kidney. But, unlike the right, it i-eceives branches 

 from the supra-renal body, the ovary, and the left oviduct in its 

 course from the kidney to the point where it unites with its 

 fellow. Thus : — 



i. The Left Ovarian Veins are numerous small tributaries 



flowing into the left efferent renal veins. 

 ii. The Left Supra-Renal Veins are a large number of small 

 branches running from the supra -renal body into the 

 efferent renal vein, to which it is closely attached. They 

 return the blood brought to that body by the supra-renal 

 portal veins, 

 iii. The Left Oviducal Vein is a large vein leaving the oviduct 

 at the level of the fimbriated funnel and flowing into the 

 efferent renal vein just in front of the supra-renal body. 

 It returns blood from the oviducal sinus. 

 A. The Left Oviducal Sinus is a wide thin -walled vessel 

 which runs from the extreme anterior end of the ovi- 

 ducal funnel backwards to about the level of the middle 

 of the corresponding kidney. It is very conspicuous in 

 injected specimens and was present in all the female 

 examples of T. natrix that I have examined, although it 

 does not appear to have been recorded in any other 

 Ophidian. 



The Post-Caval Vein (V. cava posterior, Schlemm) is formed, 

 as has been stated above, by the union of the two efferent renal 

 veins. It passes forward, dorsal to the gut, freely in the mesen- 

 tery to the posterior extremity of the liver, and then along in a 

 groove in the ventral surface of that organ to its anterior end. 

 After leaAdng the liver it runs almost straight forward, ventral to 

 the right systemic arch and unites with the right pre-caval to 

 form the larger division of the sinus venosus. Soon after its 

 origin it i-eceives veins from the right ovary, the supra-renal 

 body, and the oviduct. Thus : — 



i. The Right Ovarian Veins are similar to those of the opposite 



side. 

 ii. The Right Supra-Renal Veins also resemble those on the 

 left and return the blood gathered by the supra-renal 

 portal veins, 

 iii. The Right Oviducal Vein is like its fellow on the left and 

 comes from an oviducal sinus. 

 A. The Right Oviducal Sinits extends along the oviduct fi-om 

 the anterior end of the funnel to about the level of the 

 middle of the right kidney. 



