132 PHYSIOLOGY CHAP. 



the walls of which diverge many offshoots of various form and 

 length. The walls of the vesicula consist of a tunica mucosa, a 

 tunica musculosa, and a tunica adventitia (Fig. 25). The epi- 

 thelial cells vary in form with age; in the newly born and the 

 young child they are cylindrical, in the adult cubical and some- 

 times flattened. They are undoubtedly secretory. The secretion 

 which is found in the cavity of the vesicula is a yellowish viscous 

 substance, which, after death, or after ejaculation, takes a gelatinous 

 form, or that of granules of sago, but later becomes fluid, and 

 contains a globulin soluble in acetic acid. In animals a change 

 of form has been observed in the secretory epithelium as the 

 result of coitus, and the excitation of the secretory nerves (Stilling 

 and Akutsu). During rest it is larger and richer in protoplasm 

 than in the state of functional activity. 



Besides the function of the glands in forming a special secre- 

 tion, many physiologists have attributed to the vesiculae semi- 

 nales as to the ampullae of the epididyinis also the office of 

 reservoirs for the spermatic fluid produced by the testicles (recep- 

 taculum seminis). The question is not yet clearly settled, although 

 in more recent times it is considered of greater importance than 

 the secretory function. As to the physiological function of the 

 secretion of the vesiculae seminales it can only be affirmed that it 

 is different in different animals. According to the observations 

 of Leuckhart, in rodent animals, the secretion of the vesiculae, 

 mingling with the prostatic secretion during coitus, coagulates 

 and forms a sort of plug which occludes the vaginal opening and 

 prevents the escape of the semen, which otherwise might easily 

 happen, owing to the excessive rapidity with which coitus is 

 completed. In other animals, on account of the greater duration 

 of the retention of the penis in the vagina, there is no need for 

 the formation of a plug. In them the vesicular secretion serves 

 to dilute the testicular and to facilitate its ejaculation. But that 

 this dilution is necessary to render the sperm capable of fertilisa- 

 tion is neither proved nor probable, as Nagel justly notes. 



Tarchanoff (1887), experimenting on frogs, concluded that the 

 filling and the state of tension of the vesiculae seminales determine 

 the sexual need in the male, so that their removal or the evacua- 

 tion of their contents is sufficient to make the embrace cease 

 immediately ; and, on the other hand, the simple injection of milk 

 into the vesiculae creates artificially the sexual need (vide Vol. IV. 

 Chap. II. p. 82). Steinach, however (1894), was not able to confirm 

 these results. He noted that the esculent frogs do not possess 

 vesiculae, and in the common grass frogs, on which Tarchanoff 

 experimented, the embrace was observed several days before the 

 vesiculae were filled with secretion. He observed, moreover, that 

 when the vesiculae were extirpated before or during copulation, 

 the embrace did not always cease, and that when the female was 



