200 EDWIN J. COHN. 



meter is about 7.6 (Henderson, L. J., and Cohn, E. J., 1916). 

 But this is the hydrogen potential that has been found to be 

 most effective in increasing the length of life of spermatozoa. 

 Three experiments are reported in Table XI. It will be seen 

 that when the carbon dioxide tension is greater than one milli- 

 meter and the hydrogen potential less than 7.6, sperm are de- 

 stroyed. This is in complete agreement with what has already 

 been found with respect to the hydrogen ion concentration. 



It is not maintained that the only effect of carbon dioxide 

 upon the physiological condition of spermatozoa is brought about 

 by ionized hydrogen. On the contrary, several experiments, 

 which are unfortunately not conclusive (and are therefore not 

 reported) indicate a difference in the subsequent behavior of 

 spermatozoa that are subjected to the same hydrogen ion con- 

 centration but to different carbon dioxide tensions. The fact 

 that the total carbon dioxide production per unit concentration 

 of sperm in concentrated suspensions is less than in more dilute 

 suspensions (Table IV.) suggests that the rate at which carbon 

 dioxide is eliminated depends in some way upon the difference 

 in carbon dioxide tension between the spermatozoon and its 

 environment. 



IX. THE EFFECT OF THE OXYGEN CONCENTRATION UPON THE 

 ACTIVITY AND UPON THE LONGEVITY OF SPERMATOZOA. 



The generalization may be hazarded that whatever decreases 

 the activity increases the length of life of spermatozoa and con- 

 versely that whatever increases the activity decreases the length 

 of their life. Buller (Duller, A. H., 1902) observed the differen- 

 tial activity of spermatozoa in an oxygen gradient (see p. 175). 

 Drzewina and Bohn (Drzewina, A., and Bohn, G., 1912) have 

 demonstrated that sperm live for a long time in an oxygen-poor 

 medium. 



Drzewina and Bohn have also demonstrated that the addition 

 of KCN to sea water prolongs the life of the sperm. Loeb (1915) 

 has shown that spermatozoa are immobilized by NaCN, and it is 

 "Certain that the length of their life is thereby increased. " It is a 

 well-known fact that the unfertilized eggs of the sea urchin (in 

 fact of all marine animals) perish when they lie for some time in 



