62 



THE WAY LIFE BEGINS 



the level of the mammals, including man, is reached, the 

 sperm and egg cells are so small that they cannot be distin- 

 guished except by very high powers of the microscope. 

 See Figures 4, page 56, and 5. 



Sperm cells of animals were first seen in 1677 when the 

 microscope was improved, but it was long before their true 

 nature and purpose was understood. A sperm cell is char- 

 acteristically an elongated body with a nucleus and a thread- 

 like tail which it uses in 

 swimming. (Figure 5.) 

 They are usually found 

 in a thick fluid much 

 like the white of egg, 

 called the semen or milt. 

 Sperm cells are produced 

 in special glands, the 

 testicles, by the mother 

 sperm cells. [They are 

 called mother sperm cells 

 though they are in the 

 body of the male.] These 

 line the inner surfaces 

 of about eight hundred 

 small tubules in the 

 testis, each of which, when uncoiled, is fully two feet in 

 length. This offers a very large surface for the mother sperm 

 cells and we see how it is possible for them to produce so 

 many sperm. As the sperm are produced, they are gathered 

 into some twenty collecting tubes and pass on to the very 

 much coiled epididymis and from this through the long vas 

 deferens or spermatic duct, the shape and course of which 

 were described in the rabbit. (Figure 6.) From the spermatic 

 duct the sperms pass, when needed, through the ejaculatory 

 duct (vn, Figure 6) to the urethral canal of the penis. 

 * At the time of sexual union the sperms are deposited at the 

 mouth of the uterus or very close to it. 



* It has been long believed by physiologists that sperm cells are stored in the seminal 

 vesicles, (vi. Figure 6). Recent research, however, makes this conclusion somewhat 

 doubtful, but further investigation will be necessary before the point is definitely determined. 



FIGURE 5 



The exceedingly minute sperm cell of the human 

 male has a long tail and a flat head within which 

 is found a nucleus similar to that of the egg. 

 They are found in vast numbers in the normal 

 seminal fluid. 



