REPROD UCTION. 



885 



nutritive substance of the fluid. Prostatic secretion is viscid and opalescent, and 

 contains 1.5 per cent, of solids, comprising mainly proteids and salts. It con- 

 tributes the substance of Charcot's crystals to the semen, and their partial decom- 

 position is said to be responsible for the characteristic odor of the seminal fluid. 

 The secretion from the seminal vesicles is fairly abundant, is albuminous, and 

 in some animals at least seems to contain fibrinogen. This enables the fluid to 

 clot after its reception in the female passages, and thus to prevent loss of sper- 

 matozoa. Cowper's glands secrete a mucous fluid. By careful experiments 

 upon white rats Steinach l has shown that removal of the seminal vesicles and 

 the prostate gland, while not diminishing the sexual passion and the ability to 

 perform the sexual act, including the actual discharge of spermatozoa, prevents 

 entirely the fertilization of the ova ; removal of the seminal vesicles alone 

 markedly weakens the fertilizing power 

 of the semen. The secretions of these 

 accessory glands are essential to the mo- 

 bility of the spermatozoa, and they may 

 have other important functions. 



The Testis. The testes (Fig. 306, t) 

 are compound tubular glands with a 

 unique structure. Formed early in em- 

 bryonic life as solid structures, with the 

 seminiferous tubules (t.s) represented by 

 solid cords of cells, they remain in the 

 embryonic condition until the time of 

 puberty. Some of the cells, the mother- 

 cells of the spermatozoa, then begin 

 actively to divide, and the result of di- 

 vision with differentiation is the mature 

 spermatozoa. These latter accumulate 

 at the centre of the tubules, the walls 

 being formed largely of the dividing 

 cells or immature spermatozoa. Other 

 cells do not produce spermatozoa, but 

 seem to disintegrate and give rise to the 

 nutritive fluid and nuclear particles that 

 are found mixed with the sperm-cells. 

 From the time of puberty on, usually 

 throughout life, this cellular activity 

 proceeds, the rate and regularity proba- 

 bly varying greatly with individuals and 

 depending largely on the frequency of 

 discharge of the semen. Spermatozoa 



may be wanting in old men, but they have been found in individuals at 

 eighty or ninety years of age. The spermatozoa accumulate within the seminal 

 1 E. Steinach : Pfluger^s Archivfur die gesammte Physioloyie, Ivi., 1894. 



FIG. 306. Diagram of the male reproductive 

 organs : t, testis ; t.s, seminiferous tubules ; t.r, 

 tubuli recti ; r.v, rete vasculosum ; v.e, vasa effer- 

 entia ; e, canal of the epididymis ; v.a, vas aberrans ; 

 v.d, v.d, vas deferens ; v.s, seminal vesicle ; d.e, ejac- 

 ulatory duct ; pr, 'prostate gland ; b, urinary blad- 

 der ; C.g, Cowper's gland ; u, urethra ; pn, penis. 



