PHYSIOLOGY OF THE SPERMATOZOON 101 



pension be above a very low degree of concentration 

 the H ions thus liberated soon reach a sufficient degree 

 of concentration to decrease the movements of the 

 spermatozoa, and ultimately stop them entirely. The 

 life of the spermatozoa is thus longer in more concen- 

 trated than in more dilute sperm suspensions because 

 they are sooner inactivated by their own CO 2 and the 

 available store of energy is not used up so rapidly. 

 Spermatozoa thus inactivated can be restored to full 

 activity merely by diluting sufficiently with normal 

 sea-water. 



The effect of concentration of the sperm suspension 

 on the duration of life of the spermatozoa has been 

 measured by Cohn, who used the fertilizing power as 

 index of vitality. The following table (after Cohn) 

 gives the results of one such experiment: 



THE LENGTH OF LIFE, AS MEASURED BY THE FERTILIZING POWER, OF 

 SPERM SUSPENSIONS OF Arbacia OF DIFFERENT 

 CONCENTRATIONS 



* Percentage of eggs fertilized at age of sperm in same horizontal row. 



The eggs used for each test were always fresh. 

 The sperm suspensions were made up at the same time 

 by percentage volume of sperm to sea-water; they were 

 then allowed to age, as shown in the left-hand column, 



