134 PHYSIOLOGY CHAP. 



of spermatozoa compared with that which is observed in the 

 ejaculations which occur with moderate frequency. 



From the whole of the phenomena which we have reviewed it 

 may be concluded that probably the vesiculae seminales have no 

 great importance as regards the potentia coeundi and the potentia 

 generandi, although it cannot be denied that their secretion 

 facilitates these two functions, either by diluting the testicular 

 secretion or forming with it and with the prostatic secretion in 

 the rodents a firm coagulum which occludes the vagina and pre- 

 vents the escape of the semen, and in the other mammals and in 

 man, a glutinous coagulum which is probably not without import- 

 ance in facilitating the fertilisation of the ovum, by preventing 

 the loss of the semen through the vulva. 



III. The prostate is a solid glandular and muscular organ similar 

 in form and dimensions to a chestnut ; it is situated in the pelvis 

 and through it pass the first portion (prostatic) of the urethra, and 

 the two ejaculatory ducts (Fig. 28). 



Its physiological activity is intimately connected with the 

 sexual function ; for it atrophies in the adult after castration, and 

 if this operation be performed in infancy, the prostate does not 

 develop. In animals it increases in size, as well as the testicles, 

 at the time of rutting ; in man it grows rapidly at the beginning 

 of puberty, reaches its complete development at 25 years, and 

 preserves its dimensions unaltered up to 40-45 years ; it increases 

 more or less in size in advanced age, until it creates a somewhat 

 considerable obstacle to the regular and complete emptying of the 

 bladder (prostatism). Smooth muscular tissue prevails in the 

 structure of the prostate ; the glandular part forms scarcely more 

 than a third, or less than half of the total mass of the organ. It 

 belongs to the type intermediate between tubular and alveolar 

 glands. It is divided into a certain number (16-32) of glandular 

 units of conical form, disposed radially around the urethra, into 

 which opens their excretory duct. Each glandular unit is 

 wrapped round by a stroma, formed of smooth muscle fibres with 

 a few connective tissue fibres, elastic fibres, and vessels, and con- 

 densed at the periphery of the organ into a thick investing 

 membrane. 



The little excretory canals, fine near the outlet, increase soon 

 in diameter and present numerous tubular and alveolar diverticula, 

 which, still deeper, increase in number and size. 



The tubules and glandular vesicles are lined by a cylindrical 

 epithelium of varying height, containing granules of yellowish- 

 brown pigment (Fig. 29). Almost constantly in the adult, and 

 still more in the aged, are found in the larger vesicles of the 

 prostate gland peculiar corpuscles, spherical or elliptical, colour- 

 less or brown, of a diameter of 0'3-0'5 mm., which present the 

 reactions of amyloid corpuscles ; these readily calcify, acquiring 



