310 CIRCULATION. 



ever, in this situation in the human subject. Generally, in 

 following out the branches of the inferior vena cava, no 

 valves are found until we come to the crural vein ; but occa- 

 sionally there is a double valve at the origin of the external 

 iliac. In some of the inferior animals, there exists constantly 

 a single valvular fold in the vena cava at the openings of the 

 hepatic, and one at the opening of the renal vein. This is 

 not constant in the human subject. 1 Yalves are found in the 

 spermatic, but not in the ovarian veins. A single valvular 

 fold has been described by Dr. J. H. Brinton, at the opening 

 of the right spermatic into the vena cava. 2 There are two 

 valves in the azygos vein near its opening into the superior 

 vena cava. There is a single valve at the orifice of the 

 coronary vein. There are no valves at the openings of the 

 brachio-cephalic into the superior vena cava ; but there is a 

 strong double valve at the point where the internal jugular 

 opens into the brachio-cephalic. Between this point and the 

 capillaries of the brain, the vessels are entirely deprived of 

 valves, except in very rare instances, when one or two are 

 found in the course of the jugular. 



In addition to the double, or more rarely triple, valves 

 which have just been described, there is another variety, 

 found in certain parts, at the point where a tributary vein 

 opens into a main trunk. This consists of a single fold which 

 is attached to the smaller vessel, but projects into the larger. 

 Its action is to prevent regurgitation, by the same mechanism 

 as the ileo-csecal valve prevents the passage of matter from 

 the large into the small intestine. These valves are much 

 less numerous than the first variety. 



1 Dr. Crisp, of England, has described valves in the splenic veins in some of 

 the inferior animals. In one of the mesenteric veins of the reindeer, he showed 

 forty-two pairs of valves (New York Medical Journal, April, 1865, p. 67). 



3 Description of a Valve at the Termination of the Right Spermatic Vein 

 in the Vena Cava, with Remarks on its Relations to Varicocele. By JOHN H. 

 BRINTON, M. D. American Journal of the Medical Sciences, July, 1856. The 

 presence of this valve, according to Dr. Brinton, explains the more frequent oc- 

 currence of varicocele on the right side. 



