C. R. AUSTIN AND M. W. H. BISHOP 73 



used for inseminating cows, the resulting incidence of concep- 

 tion was approximately the same as that which had previously 

 been obtained with ejaculated spermatozoa from the same bulls 

 (Lardy and Ghosh, 1952). The fact that the spermatozoa in the 

 epididymis and vas deferens are almost motionless but become 

 vigorously active when they make contact with the accessory 

 secretions, much as sea urchin spermatozoa do when shed into 

 sea water, suggests that activation of spermatozoa is the only 

 important function of seminal plasma, other than the carriage of 

 the spemiatozoa from male to female tracts. 



The mechanism of activation is little understood, but it is evi- 

 dently not of a specific nature. It may be due in part, at least, to 

 the dilution of an inhibitory substance (Bishop and Salisbury, 

 1955a,b) similar in its action to that of potassium in trout and 

 salmon semen (Rothschild, 1951a), or of zinc in echinoderm 

 semen (Fujii, Utida, and Mizuno, 1955). Lardy and his associ- 

 ates, on the other hand, claim that the respiration and aerobic 

 glycolysis of bovine spermatozoa are stimulated at ejaculation 

 by a specific activator, believed to be a sulfite or sulfhydryl com- 

 pound, that has the effect of reducing the metabolic efficiency of 

 these cells as measured by the Meyerhof oxidation quotient 

 (Lardy, Ghosh, and Plant, 1949; Lardy, 1953). Gunn (1936) 

 noted activation of epididymal spermatozoa upon dilution and 

 aeration. Bishop and Matthews (1952) report that quiescence of 

 spermatozoa in the vas deferens is associated with very low oxy- 

 gen tensions and a deficiency of glycolyzable substrate, but not 

 with narcotic accumulations of lactic acid or carbon dioxide. 

 They conclude that oxygen is the principal activating factor, an 

 observation in agreement with Rothschild's (1948) findings on 

 the activation of sea urchin spermatozoa. Electrolytes are also 

 known to stimulate spermatozoon motility ( Milovanov, 1934a,b ) , 

 and they probably play an important part in the activation phe- 

 nomenon. 



Both in mammalian- and echinoderm spermatozoa increased 

 dilution leads to increased physical and metabolic activity, but 

 to decreased survival of the spermatozoa (Gray, 1928; Salisbury, 



