Chemical and Physical Properties of Semen 43 



(1-28) considerably exceeds that of the erythrocytes (11) and other 

 cells of the animal body. As already mentioned (p. 8), Lindahl 

 and Kihlstrom (1952) believe that the wide range of variations in the 

 specific gravity of ejaculated bull spermatozoa (1-240-1 -334) is due 

 to the variable proportion of 'ripe' (heavier) and 'unripe' (lighter) 

 sperm cells in semen. However, whereas the specific gravity of the 

 sperm cell is due to the highly condensed nuclear and protoplasmic 

 protein constituents, the specific gravity of the seminal plasma is the 

 direct outcome of the actual osmotic pressure exerted by electrolytes 

 and is thus related to the depression of the freezing point. 



Determinations of the osmotic pressure in terms of freezing point 

 depression have been carried out in the semen of several species and 

 the following data (in centigrade) are available: man 0-55-0-58, bull 

 0-54-0-73, ram 0-55-0-70, stallion 0-58-0-62, jackass 0-56-0-62, boar 

 0-59-0-63, dog 0-58-0-60, rabbit 0-55-0-59 (Slovtzov, 1916; Roem- 

 mele, 1927; Milovanov, 1934; Bernstein and Shergin, 1936; Zagami, 

 1940; Salisbury, Knodt and Bratton, 1948; Nishikawa and Waide, 

 1951). It would seem that generally, more reliance should be placed 

 on results obtained with seminal plasma than with whole semen. 

 More recently, Rothschild and Barnes (1954) carried out freezing 

 point determinations on forty samples of seminal plasma from ten 

 bulls of different breeds, and obtained a mean value of 0-53 with a 

 standard error of 0-005. 



The electrolytes in the seminal plasma are those made available 

 by the secretions of the male accessory organs. Additional informa- 

 tion on the content of the inorganic constituents in semen is sum- 

 marized in Table 4, but again, owing to the variable composition of 

 semen, the chemical data relating to whole semen must be taken with 

 due reservations. 



The interrelations between the various ions in semen differ from 

 those existing in blood in several respects, but most perhaps because 

 of the presence of a much higher concentration of extracellular 

 potassium and a correspondingly lower content of sodium. Miescher 

 (1897) who was the first to examine systematically the chemical 

 composition of salmon semen, found in the ash prepared from the 

 seminal plasma (parts/100): 51-0 NaCl, 8-2 KCl, 140 K2SO4, and 

 26-8 Na.COa. In the trout, Schlenk (1933) recorded a value of 80 mg. 

 K/lOO ml. semen. In the sea-urchin {Echinus esculent us) Rothschild 



