282 ANIMAL AGGREGATIONS 



4. The relatively long life of concentrated suspensions is not due 

 to the narcotic effect of accumulated CO2 but is the result of an 

 incomplete state of activation on the part of each spermatozoon. 



MASS PHYSIOLOGY OF MAMMALIAN SPERM 



The experiments reported so far have dealt with spermatozoan 

 studies in those sea-dwelling animals where the sperm are shed 

 freely into the sea-water and where fertilization occurs in this me- 

 dium. There is a small amount of data at hand concerning the 

 physiology of mammalian sperm where fertilization takes place 

 within the body of the female after introduction by artificial or 

 natural means. It has already been indicated that in regard to 

 resistance to high temperatures the relation between volume of 

 sperm and degree of resistance is similar in the two types. The 

 work of Lloyd- Jones and Hayes (191 8) and of Walton (1927) allow 

 these comparisons to be carried further. The latter performed ex- 

 periments upon the physiology of the spermatozoon, using insemina- 

 tion as a test for fertility. One of the variables found to enter is that 

 of the mass of sperm present per given volume of mecHum. 



Walton, in his work, obtained spermatozoa from a buck rabbit 

 killed by a blow behind the ears. The abdomen was opened im- 

 mediately, the testes removed, and the cauda epididymi were opened 

 in about 5 cc. of 0.15 NaCl solution. This gave a dense suspension 

 of spermatozoa. After examination under the microscope to check 

 for motility, these were diluted in ascending powers of 10. 



Doe rabbits were allowed to copulate with vasectomized males to 

 insure ovulation and were then artificially inseminated immediately. 

 Directly thereafter the densities of the sperm solutions used were 

 determined with the aid of a haemocytometer for those between 

 10^ and 10^, and the others were estimated from the dilution in 

 comparison with those counted. The results from 130 experiments 

 performed are given in Table XXXII . 



Walton recalculated the data obtained by Lloyd- Jones and Hayes 

 from studies on the effects of insemination after excessive sexual 

 activity of male rabbits. The results are shown in Table XXXIII. 



Even in these internal impregnations a large number of spermato- 



