40 The Biochemistry of Semen 



Squiers, Bogart and Oloufa, 1951; Ortavant, Dupont, Pauthe and 

 Roussel, 1952; Campbell, Hancock and Rothschild, 1953); micro- 

 scopic assessment of the degree of motility, either directly in semen 

 (Harvey and Jackson, 1945; McLeod, \9A6a; Emmens, 1947; Farris, 

 1950) or by the 'cervical mucus penetration test', in which a drop of 

 semen is placed on the microscope slide next to cervical mucus and 

 the passage of spermatozoa through the mucus is followed by micro- 

 scopic observation (Barton and Wiesner, 1946; Harvey and Jackson, 

 1948). The determination of the concentration of motile spermatozoa 

 in a semen sample is generally held to be the criterion most clearly 

 correlated with the actual fertility rate; but even this relationship 

 occasionally fails to give a true picture, and motile spermatozoa 

 are by no means always fertile. 



Physico-chemical methods of semen analysis depend on the deter- 

 mination of a wide range of physical, chemical and metabolic 

 characteristics of semen, related to the physiological function of the 

 sperm and the seminal plasma. Here belong methods for the 

 measurement of certain optical properties of semen such as the 

 light-scattering and light-absorption power, electrical conductivity 

 and impedance changes; specific gravity, osmotic pressure; hydrogen 

 ion concentration, buffering capacity; occurrence of semen-specific 

 metabolites such as fructose, citric acid, ergothioneine, and inositol, 

 and various enzymes such as hyaluronidase and certain phospha- 

 tases; and finally, the rate of anaerobic and aerobic metabolic 

 processes in semen expressed in terms of fructolysis index, respira- 

 tion rate or methylene-blue reduction time. 



Optical and electrical properties of semen 



An optical property closely related to sperm concentration is the 

 turbidity of semen. In the past, determinations of sperm concen- 

 tration were based on microscopic sperm-counts but more recently 

 these have been partly replaced by turbidimetric measurements, 

 which can be carried out quickly with suitably diluted samples either 

 in a visual comparator by direct comparison with opacity standards, 

 or in a photoelectric absorptiometer, to provide values for the rela- 

 tive light transmission of semen (Burbank, 1935; Comstock and 

 Green, 1939; Henle and Zittle, 1942; Salisbury et al. 1943; Roth- 

 schild, 19506). The turbidimetric methods, however, it must be 



