MASS PHYSIOLOGY OF SPERMATOZOA 285 



has been shown by Cohn to be what one would expect from the pH 

 changes known to accompany this treatment. The third explana- 

 tion seems to be well established for a number of animals and is 

 supported by various observers. If this be sound, the movement 

 hypothesis — the first and in a modified form the seventh on our 

 list — is not closely pertinent in the problem of functional longevity, 

 although still of value in the matter of total longevity. There seems 

 to be no doubt but that self-produced CO2 slows down metabohc 

 processes of crowded spermatozoa, and so delays their final loss of 

 fertilizing power; but following the experience of Drzewina and 

 Bohn and of Gray, with controlled CO2 tensions, it is no longer pos- 

 sible to believe that this is the whole story. The autoprotective 

 secretion hypothesis is not strongly supported by direct evidence. 

 A final decision concerning the applicability of electrical phenomena, 

 as advanced in our sixth hypothesis, must await the further develop- 

 ment of biophysics in this field. 



Finally, we may pause for a moment to consider the justification 

 for bringing the mass relations of spermatozoa into a discussion of 

 the physiology of numbers as a foundation for the formulation of a 

 consistent view of general sociology. If the phenomena with which 

 we have been dealing have general rather than special significance, 

 we shall expect them to appear wherever there are collections of 

 living material, whether these are gametes or zygotes or the products 

 of zygotes. The advanced state of investigation into the physiology 

 of the spermatozoa allows us to make this an important test case of 

 the general application of the relationships already found to hold 

 rather generally throughout the animal kingdom. The fact that 

 they also operate here strengthens by that much our belief in their 

 general applicability. A similar inquiry into the same set of rela- 

 tions in the culturing of bacteria and in tissue culture has shown 

 that in those fields also there are definite protective values in opti- 

 mum mass relations, and that, as in many animal relationships, 

 the optimum usually does not coincide with the minimum popula- 

 tion either of spermatozoa, of bacteria, or of cells in tissue culture. 



