352 



THE ORGANS 



centrosomes, or incompletely, forming a dumb-bell-shaped body. The nuclear 

 material becomes very compact and passes to one end of the cell, forming the 

 bulk of the head. Both centrosomes help to form the body. They first become 

 disc-shaped. The one lying nearer the centre of the cell becomes attached to the 

 posterior end of the head as the anterior end-knob, the other takes a position a 

 little more posteriorly as the posterior end-knob and from it grows out the axial 

 filament. Some of this centrosome passes to the posterior limits of the body 

 and there becomes the end ring. As the two parts of this centrosome separate 

 the delicate cytoplasm between them forms the spiral fibres. During these 

 changes the axial filament has been growing and projects beyond the limits of 

 the cell. Most of the cytoplasm of the spermatid is not used in the formation 

 of the spermatozoon, but is cast ofT and degenerates. A small amount is used 

 for the sheath of the body, and for the galea capitis. The sheath of the main 

 part of the filament appears to develop from the filament itself. Atypical 

 spermatozoa are not infrec}uent. Thus are found very large, or very small 

 types, or spermatozoa with several tails attached to a single head or less 

 commonly several heads with only one tail. 



The significance of the different parts of the spermatozoon has been brought 

 out in describing its development. From this it is seen that the spermatozoon, 

 like the mature ovum, is a true sexual element with one-half the somatic number 

 of chromosomes. The head and body, containing the chromatin and the centro- 

 somes, are the parts of the spermatozoon essential to fertilization. The acro- 

 some is an accessory which in some forms at least aids the spermatozoon in 

 attaching itself to and in entering the ovum. The tail is an accessory structure 

 upon which depends the motility of the spermatozoon. In the lumen of the 

 seminiferous tubules very little motion is observable, only after they have 

 become a part of the semen (p. 349) does their motion become active. This 

 activity is retained in the fluids of the female generative tract. Considering 

 their minuteness, their speed is considerable, having been estimated at from 1.5 to 

 3.5 mm. per minute; enough to allow them to ascend through uterus and oviduct 

 against the adverse action of the cilia. When in a favorable environment, 

 such as the fluids of the female generative tract, the spermatozoon is capable 

 of living for some time after leaving the testicle. Living spermatozoa have been 

 found in the uterus or tubes three and a half weeks after coitus. 



TECHNIC 



(i) For the study of the general topography of the testis, remove the testis of 

 a new-born chUd, make a deep incision through the tunica albuginea in order to 

 allow the fixative to penetrate quickly, and fix in formalin-Miiller's fluid (technic 

 6, p. 7). Antero-posterior longitudinal sections through the entire organ and in- 

 cluding the epididymis should be stained with haematoxylin-picro-acid-fuchsin 

 (technic 3, p. 21) or with haematoxylin-eosin (technic i, p. 20) and mounted in 

 balsam. 



(2) The testis of a young adult is removed as soon after death as possible, is 

 cut into thin transverse sUces, which include the epididymis, and is fixed in forma- 

 lin-M tiller's or in Zenker's fluid (technic 10, p. 8). Select a slice which includes 

 the head of the epididymis, cut away the anterior half or two-thirds of the testis 



