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A TEXTBOOK OF PHYSIOLOGY 



in number). These form the epididymis, the tubules gradually uniting 

 to form the vas deferens. The vas deferens is associated with the 

 nerves and bloodvessels of the testis in forming the spermatic 

 cord. 



Apical body, 

 or acrosome 



Nucleus 



End knob 

 Middle piece 



Envelope of 

 tail 



Axial fila- 

 ment 



The Accessory Glands. The exact func- 

 tion of the accessory glands is not quite 

 clear. The accessory secretions, mixed with 

 the testicular secretion, are believed to aid 

 the movements of the spermatozoa, prob- 

 ably owing to their alkalinity. It is stated 

 that extirpation of the prostate causes 

 sterility, owing to the withdrawal of its 

 secretion. The prostatic secretion is serous 

 and milky in appearance, amphoteric in 

 reaction. That the accessory apparatus is 

 of value is shown by the fact that it 

 develops at puberty, and this development 

 is prevented by early castration. Castration 

 after puberty leads to an atrophy of the 

 aparatus. 



The Seminal Fluid. -The seminal fluid 

 consists of the external secretion of the 

 testes combined with the secretion of the 

 glands of the vas deferens, of the glands 

 of Cowper, and of the prostate and vesiculae 

 seminales. It is a whitish viscous fluid, 

 alkaline in reaction, contains about 90 per 

 cent, of water, and is of a specific gravity 

 of about 1034. The inorganic substances 

 (0-9 per cent.) consist chiefly of sodium 

 chloride and the phosphates of calcium 

 and magnesium. The organic bodies of 

 the semen consist of nuclein attached to 

 protamine, some albumin and proteose, 

 fats, and the lipoids lecithin and cho- 

 lesterin. 



The spermatozoon is the active agent 

 of reproduction contained in the male 

 ejaculation. It varies in form with dif- 



FIG. 472. DIAGRAM OF SFER- ferent types of animal, but in all higher 



MATOZOON. (Redrawn from forms consists essentially of a head piece, 



!tc -> a middle piece, and a flagellum-like tail 



piece. In man the head is pear-shaped 



(Fig. 472). Movements are made by the lashings of the flagellum- 

 like tail. The movements* are increased by weak alkali, inhibited 

 by acid or distilled water. 



The penis serves the purpose of introducing the seminal fluid in 

 the sexual apparatus of the female. It consists largely of erectile 



End piece 



