XXI. 



THE MALE GENITAL TRACT. 



THE male genital organs are : first, the testes, which are des- 

 tined to produce the fructifying principle of reproduction, 

 the semen or sperm,; second, the vas deferent and seminiferous 

 vesicles, whose office is to carry and store it up ; and third, the 

 penis, for transferring the spermatic fluid into the female genital 

 organs. The prostatic and Cowper's glands are accessory organs, 

 which produce mucus mainly. The spermatozoids are the essen- 

 tial fructifying element of semen. These are bioplasson forma- 

 tions, varying greatly in size and shape in different animals. In 

 man they are pin-shaped, with a thickened head and a thread-like 

 tail, which at its point of attachment to the head is slightly 

 conical, exhibiting either a pear-shaped, a knob-like, or a double 

 lobate enlargement. The head is of a roundish, ovoid, or conical 

 shape, the point representing the free proximal end. Their length 

 is, on an average 0.0040 mm. Sometimes the whole formation ap- 

 pears homogeneous, and of a high luster. Sometimes a vacuole is 

 observed in the head, and sometimes a delicate reticular struc- 

 ture can be traced throughout the thickened portions. Sper- 

 matozoids, when in a fresh condition, are in an active wind- 

 ing or spiral motion, executed by the tail, through which motion 

 the head is rotated with a boring movement, and at the same 

 time the spermatozoid changes its place. This motion is favored 

 by slightly alkaline media, dilute solutions of table-salt, and of 

 phosphate of soda ; acids, on the contrary, soon produce rest. 



Spermatozoids retain their shape after having lost their 

 mobility for a long while, even after they have been allowed 



