THE MALE AND FEMALE REPRODUCTIVE ORGANS 1125 



well as by the action of the cilia-like appendages of some of its lining 

 cells. 



The spermatozoon is a complete cell, consisting] of a nucleus and cytoplasm. 



In many cases, however, it is - nn nnf . times smaller than the germinal cell of the 



iUUfUUU 



opposite sex, the ovum. It has the appearance of a minute tadpole and presents a 



nucleus which forms the principal portion of its conoid and slightly flattened head, 



an apical piece or acrosome at the front of the head, a middle piece directly behind 



the head, and a long slender tail or flagellum. Its total length measures from 



50 to 80 fj,. 1 Physiologically considered, its nucleus derives its importance from the 



fact that it contains the chromatin, while its 



middle piece represents the centrosome 



element which serves as the stimulus to 



division. Its apical piece is of importance 



because it enables the spermatozoon to bore 



its way into the ovum, and its tail because 



its contractile substance furnishes the motile 



power by means of which this chemical 



complex is enabled to reach the passive 



ovum. 



The formation of spermatozoa be- 

 gins at the time of puberty or sexual 

 maturity, i.e., in temperate climates at 

 about the fifteenth year. Some of 



FIG. 535. FIG. 536. 



FIG. 535. DIAGRAM TO REPRESENT THE PROGRESSIVE SERPENTINE MOVEMENTS OF 

 THE TAIL OF THE SPERMATOZOON. 



FIG. 536. DIAGRAM OF THE BLADDER, PROSTATE GLAND, ROOT OF PENIS, ETC. 



Cl, Part of base of bladder covered by peritoneum, separated by a dotted line from a 

 triangular space left uncovered by that membrane; V, ureter; S.V, seminal vesicle; 

 ED, ejaculatory duct; P, prostate; M, membranous part of the urethra; B, bulb; C.S, 

 corpus cavernosum urethrse; C, crus penis; C.G, Cowper's gland. (J. Symington.) 



the adjunct powers of the sexual mechanism, however, may have 

 been active for some years before this time; for example, the erec- 

 tion of the penis and sexual desire. Thus, the only definite sign of 

 maturity is the presence of fully developed spermatozoa in the semen. 

 This change is associated as a rule with a greater stability of the body 

 as a whole. The voice becomes deeper, owing to a more rapid growth 

 1 Eberth, in Bardeleben's Handb. der Anatomic des Menschen, Jena, 1904. 



