The Semen and Spermatozoa 77 



4. The Semen and Spermatozoa 



The satisfactory examination of the male genitalia ordi- 

 narily involves an examination of the semen. This is best 

 accomplished by causing the male to copulate with a female 

 and removing immediately some of the semen from the 

 vagina. This may be conveniently attained by introducing 

 a sterile swab, like that used in diphtheria, deeply into the 

 vagina. Then withdraw the swab and from it make a smear 

 on an ordinary slide, apply a cover glass and examine under 

 moderate magnification. If the examination is made in a 

 warm room and the preparation is kept moist by adding a 

 few drops of physiologic salt solution, healthy spermatozoa 

 continue to move vigorously during a period ample for study 

 of the living cells. If the semen is kept warm and moist, it 

 may be carried some distance and examined after several 

 hours. It is best, however, to examine the semen as to mo- 

 tility soon after ejaculation. 



The quantity of semen ejaculated is likewise of funda- 

 mental importance in judging the fertility of a sire. While 

 technically but one spermatozoon is necessary for the fer- 

 tilization of an egg, there are physiologically many millions 

 of spermatozoa for each ovum. The luxurious numbers 

 serve as a safeguard against their total destruction during 

 the hurried migration from the vagina to the ovary. Not 

 only is it important that great numbers of spermatozoa shall 

 be present in order to make it certain that at least one vigor- 

 ous cell will reach the ovum, but great numbers constitute, 

 under certain limitations, an indication of sexual health and 

 vigor. The amount of semen needs to be determined by some 

 form of approximate measurement. In horses and cattle 

 the vagina of the female may be well washed out with sterile 

 salt solution or with a 0.257; chlorazene solution which dis- 

 solves the vaginal mucus, followed by the salt solution, and 

 by inserting the well disinfected hand, the animal may be 

 caused to eject all fluid or it may be ladled out with the 

 hand. If the male is then caused to copulate with her, the 

 contents of her vagina may be at once ladled out of the 



