ACTIVITIES OF THE MALE REPRODUCTIVE SYSTEM 33 



also as an aid for this event. Modern research emphasizes, therefore, that the 

 work of the male reproductive system is not complete until this contact is 

 made. 



b. Coagulation of the Semen 



In many mammalian species, the semen tends to coagulate after its dis- 

 charge from the male system. In the mouse, rat, guinea pig, opossum, rhesus 

 monkey, etc., the semen coagulates into a solid mass, the vaginal plug, once 

 it reaches the vagina of the female. The probable function of the vaginal 

 plug is to prevent the semen from seeping out of the vagina. The formation 

 of this plug may be due to a protein present in the contents of the seminal 

 vesicle which comes in contact with the enzyme, vesiculase. In the rat and 

 guinea pig this catalyst probably is produced by the ''coagulating gland," a 

 specialized structure associated with the seminal vesicles in these forms. Some 

 of it also may come from the prostate. 



Coagulation of the seminal fluid also occurs in man, stallion, and boar but 

 it is entirely absent in the dog, bull, and many other animals. Human semen 

 coagulates immediately after discharge but liquefies a short time afterward. 

 This liquefaction may be due to the presence of two enzymes, fibrinogenase 

 and fibrinolysin, found in human semen and both derived from the prostate. 

 These enzymes are found also in dog semen. In the latter their property of 

 inhibiting blood coagulation may be of use where considerable amounts of 

 blood may be present in the female genital tract at the onset of full estrous 

 conditions. Another important contribution of the prostate gland is citric acid. 

 Its role is not clear but it may enter into the above coagulation-liquefaction 

 process (Mann, '50, p. 348). 



c. Hyahironidase 



Various enzymes have been demonstrated to be present in the semen of 

 certain invertebrates and vertebrates. One such enzyme is hyaluronidase which 

 appears to be produced in the testes of the rat, rabbit, boar, bull, and man. 

 It is not found in the testes of vertebrates below the mammals. Its specific 

 function is associated with the dispersal of the follicle cells surrounding the 

 egg; in so doing it may aid the process of fertilization in mammals. 



d. Accessory Sperm 



One sperm normally effects a union with the egg in fertilization. Accessory 

 sperm may enter large-yolked eggs, but only one is intimately involved in 

 the union with the egg pronucleus. However, what is meant by accessory 

 sperm here is the large number of sperm which normally clusters around 

 the egg during the fertilization process in many animal species. A suggestion 

 of a function for these accessory sperm follows from the fact that hyaluroni- 

 dase may be extracted from the semen, presumably from the sperm them- 



