MASS PHYSIOLOGY OF SPERMATOZOA 



283 



zoa is apparently necessary to insure fertility, and there is a signifi- 

 cant decrease in percentage of fertile matings as the artificial or 

 natural sperm suspensions become less dense. In the artificial in- 

 seminations just summarized a mark of decline came when the 

 number of spermatozoa was less than 10^ per cc, and complete steril- 

 ity occurred when this value fell below about lo-* per cc. In the 

 series with overworked males the point of complete sterility was not 



TABLE XXXII 

 Number of Sperm per 3 Cc. Placed in Vagina of Doe 



TABLE XXXIII 



Copulation 



Volume, cc 



Density per cc 



Total number of 

 sperm ejaculated . 



Percentage of fertil- 

 ity 



0.34 

 104. 5X10'' 



35.6X10^ 



72 .09 



0.21 

 39.5 Xio" 



8.4 X106 



61. 1 



0.22 

 14.7 Xio^ 



3.2 Xio'' 

 41 -37 



0.13 

 4-2 Xio"^ 



0.6 Xio« 

 41 -37 



0.1 



35 Xio« 



0.3 Xio^ 

 35-55 



reached. It is of interest that the size of the litters is reduced after 

 the first, fifth, and fifteenth service. 



In the latter series there are complicating factors other than 

 density of the sperm population. Thus, there is not only a decrease 

 in the density but also in the percentage of functionally mature 

 sperm, a decrease in progressive motility, and a decrease in the 

 duration of the motility of the sperm. That the latter effects are 

 not due to mere dilution is shown by the fact that similar sperm 

 diluted with 10 times its volume of isotonic solution showed greater 

 duration of longevity than did sperm in the natural medium at 

 the density existing when ejaculated. The probable cause of this 

 phenomenon is that in the natural semen the by-products of me- 

 tabolism and of developing bacteria more quickly reach a harmful 



