The Vascularization of the Human Testis. 473 



Mall several years ago advanced a theory as to the presence of 

 certain units of the blood system which may or may not be peculiar 

 to the organ in which they* are found and which correspond to 

 the histological or structural unit of the organ. These units are 

 composed of small branching blood vessels which pass into capil- 

 laries, the blood from which is collected into small veins. This theory 

 of vascular units may be briefly summed up in the statement "sim- 

 ilar blood supply to similar histological units." These vascular 

 units have since been proved to be present in the liver, spleen and 

 adrenal, but in the testis of the pig I could make out no definite 

 units. In man, however, the lobular arrangement is less complex, 

 and I was enabled to make out vascular units which correspond to 

 units of structure and which repeat themselves similarly throughout 

 the organ, the one bearing a definite and constant anatomical relation 

 to the other. 



To determine the units, a testis, after receiving an arterial and 

 venous injection, Mas placed in 95 per cent alcohol until well 

 hardened, then cut into blocks measuring about .5 cm. in thick- 

 ness and later cleared in 1 per cent, potassium hydroxide. In this 

 way the tubules remained firm and the lobules could be teased 

 out with their vascular supply. Wlien placed in 20 per cent glycer- 

 ine the vascular units were clearly defined. 



Fig. 8 indicates the arterial supply to a lobule. There is a 

 very profuse anastomosis between the arteries enclosing the lobule 

 and each lobule receives blood from two or more ascending arteries 

 and a like number of descending arteries which are branches of 

 the capsular arteries. From the vessels enclosing the lobules small 

 arterioles are given off which in turn encircle the tubules ending 

 in a plexus around them. Thick microscopic sections of the injected 



Fig. 8. — Arterial supply of lobule of human adult testis. Injected with 

 celloidin, cleared in 1 per cent KOH and glycerine. The testis was then 

 cut into large pieces and the lobules teased out. C, capsule showing capsular 

 artery on inner side of albuginea ; M., mediastinum. 



Fig. 9. — Microscopic section of adult human testis. Injected with 4 per 

 cent celloidin to show arterial and capillary blood supply to tubules. Sec- 

 tions cut to 200 microns in thickness, stained in H. and E. and cleared in 

 creosote, x ^0. 



