152 The Biochemistry of Semen 



no fructose in the seminal plasma; the possibility, of course, must 

 not be overlooked that there may be in dog semen some other sub- 

 stance of nutrient value to the spermatozoa. Redenz (1933) has 

 shown that bull spermatozoa glycolyse glucose, fructose, and man- 

 nose to lactic acid, and that the presence of these sugars, but not 

 that of sucrose, lactose, or glycogen, is beneficial to sperm motility. 

 His findings were confirmed by others and it has since become 

 an established fact that the metabolism of spermatozoa in several 

 mammalian species including man, ram and bull, is predominantly 

 of a glycolytic character (Ivanov, 1935; Shergin, 1937; Comstock, 

 1939; MacLeod, 1939, 19436; Lardy and Phillips, \9A\a\ Moore and 

 Mayer, 1941; Henle and Zittle, 1942; Ross, Miller and Kurzrok, 

 1941; Salisbury, 1946). 



Sperrnatozoa obtained directly from the epididymis of a bull, 

 ram, or boar, resemble washed ejaculated sperm in that they are 

 incapable of survival under purely anaerobic conditions. While in 

 the epididymis, the spermatozoa have no access to fructose and are 

 immotile; the onset of motiUty coincides with their passage along 

 the male genital tract and contact with the seminal plasma. The acti- 

 vating influence of fructose on previously immotile spermatozoa 

 can be convincingly demonstrated in a simple manner. Fresh epi- 

 didymal spermatozoa are suspended in bicarbonate-Ringer solution; 

 two 'hanging drops', one of the suspension and another, a little 

 further away, containing a 1 % solution of fructose in bicarbonate- 

 Ringer solution, are placed on the underside of a cover-sUp; to 

 observe the motility of the sperm under the microscope, the cover- 

 slip is fixed to the top of a small glass chamber in which one can 

 create anaerobic or aerobic conditions by passing through the cham- 

 ber a gas mixture of 95% N2-5% CO2 or 95% 02-5% CO2. In the 

 absence of oxygen, the spermatozoa can be seen to be almost com- 

 pletely immotile, but when the two drops are brought together the 

 sperm movement begins and continues for a long time. Aerobically, 

 the effect of fructose is less striking because oxygen induces endo- 

 genous respiration and this in itself provokes motility in epididymal 

 spermatozoa. However, even in the presence of oxygen, fructose 

 still has some influence owing to the process of aerobic fructolysis. 



Under anaerobic conditions, the final product of sperm fructolysis, 

 lactic acid, cannot be oxidized further. In the presence of oxygen, 



