Chemical and Physical Properties of Semen 45 



any rate never more alkaline than pH 7-3, whereas in sterile rams the 

 pH value may reach 8-6. However, the rate at which acidity increases 

 after ejaculation is much more significant for the assessment of 

 semen than the initial pH value, because it is related directly to the 

 actual glycolytic activity of the spermatozoa, and indirectly to 

 sperm density and motility. In bull and ram semen this correlation 

 is said to be so close that the decrease in pH on incubation can 

 serve as an additional indicator of semen quality (cf. Anderson, 

 1945; Laing, 1945; Reid, Ward and Salsbury, 1948Z)). As a matter 

 of fact, however, the significance of this method is limited because 

 as the pH value falls, the semen becomes too acid for spermatozoa 

 to maintain their motility and metabolism. 



Some of the effects which are due to variations in hydrogen ion 

 concentration in semen will be discussed in the next chapter; here 

 we shall concern ourselves with the buffering capacity of semen 

 which has been the subject of some interesting work, especially in 

 bull and human semen (Shergin, 1935; Smith and Asdell, 1940; 

 Easley, Mayer and Bogart, 1942; Sheldovsky, Belcher and Leven- 

 stein, 1942; Willett and Salisbury, 1942; Anderson, 1946«). On the 

 whole, bull semen is more highly buffered on the acid than on the 

 alkaline side, and its normal buffering capacity depends mainly 

 upon citrate and bicarbonate, but not phosphate. Anderson used 

 107 specimens of seminal plasma from normal bulls and measured 

 their buffering power by adding 005 ml. OIn-HCI to 01 5 ml. 

 plasma, and determining the pH with the help of a glass electrode, 

 before and after acid addition; the decrease in pH value obtained 

 in this way was l-84±0038. He also investigated the relationship 

 between buffering capacity and the period for which sperm motility 

 of 70% and over, was maintained; semen specimens which kept up 

 this motility for 24 hr. and upward, all had a good and fairly uniform 

 buffering capacity (decrease in pH=l-74), but those with a smaller 

 degree of motility at 24 hr. had a poorer buffering capacity (decrease 

 in pH=200). 



Metabolism of semen, and its relation to sperm density and motility 



The two chief metabolic processes of semen, namely fructolysis 



and respiration, are both a direct outcome of the metabolic activity 



of the sperm cells; their rate is determined largely by the number 



