THE MALE HORMONE 



which take many days to be carried through its whole length. 

 During this journey they have time to mature. If one ex- 

 amines under the microscope sperm cells taken from the 

 epididymis of a freshly killed animal, they are found to be 

 in active motion, whereas those taken from the testis are 

 motionless. There has been a good deal of discussion, not 

 yet settled, as to whether the activation of the sperm cells 

 is brought about by stimulatory substances secreted by the 

 cells lining the tube of the epididymis, or merely by the 

 process of maturing. Regardless of this question, it is at 

 least certain that the epididymis is a favorable place for the 

 sperm cells, for when experimenters have tied off its tube 

 in two places, leaving sperm cells trapped between the liga- 

 tures, the cells have been found to remain active for two weeks 

 or more. 



Emerging from its coiling in the epididymis, the seminal 

 canal becomes less tortuous and finally runs directly upward 

 under the skin toward the groin, as shown in Fig. 30. This 

 part of the system is called the seminal duct or vas deferens. 

 The two ducts (one from each testis), pass over the front 

 of the pelvic bones to enter the interior of the pelvis. Pro- 

 ceeding down the side and rear of the pelvis the two ducts 

 approach each other under the urinary bladder. Before 

 they unite each of them gives rise to a small saccular off- 

 shoot or branch, the seminal vesicle. These vesicles are club- 

 shaped hollow structures, really side branches of the seminal 

 duct. They are each about 10 centimeters (4 inches) long, 

 but folded to half that length as they lie in place. They 

 are glands of external secretion, producing in their cavities 

 a clear gelatinous substance which becomes part of the 

 seminal fluid. There is an old notion, hardly yet cleared out 

 of the medical textbooks, that the seminal vesicles are reser- 

 voirs for sperm cells, but the fact is that sperm cells are not 

 normally found in them. 



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