The Two Components of Semen 23 



of several species, including man (20 mM), bull (100 mM) and 

 boar (300 mM). In the latter, the ionic equilibrium on the cationic 

 side is set up chiefly by potassium, with citric acid as the main anion; 

 the concentration of sodium is much less than that of potassium; 

 chlorides are conspicuous by their almost total absence, a phe- 

 nomenon infrequently encountered in other normal body fluids 

 (Table 3). Another unusual feature of the boar vesicular secretion is 

 its high content of inositol which varies from 2 to 3% and accounts 

 for something like one-third of the total dialysable material; inositol 

 together with citrate, contributes substantially to the osmotic pres- 

 sure of the vesicular secretion (Mann, 1954). 



The reducing power of the vesicular secretion is one of its most 

 characteristic chemical properties. Two kinds of reducing sub- 

 stances are present. One group is made up of substances which 

 are capable of reducing silver nitrate, iodine and 2 : 6-dichlorophenol 

 indophenol in the cold. They are always present in the protein-free 

 filtrate from the vesicular secretion and seminal plasma but 

 their chemical nature varies from one species to another. At 

 one time, the reducing property was generally attributed to 

 ascorbic acid, in the secretions of the guinea-pig (Zimmet and 

 Sauser-Hall, 1936; Zimmet, 1939), bull (Phillips, Lardy, Heiser and 

 Ruppel, 1940; Jacquet, Cassou, Plessis and Briere, 1950) and man 

 (Nespor, 1939; Berg, Huggins and Hodges, 1941). According to 

 Phillips and his co-workers, bulls of high fertility produce semen 

 containing 3 to 8 mg. ascorbic acid per 100 ml., whereas low-fertility 

 bulls may have less than 2 mg./lOO ml.; these workers have also 

 claimed that in certain bulls it was possible to enhance the fertility 

 by parenteral administration of ascorbic acid. More recent studies, 

 however, based upon chemical methods of purification and identi- 

 fication, have proved that ascorbic acid rarely accounts for the total 

 reducing power of semen towards dichlorophenol indophenol. In 

 the boar especially, ascorbic acid has been shown by Mann and 

 Leone (1953) to account but for a small fraction of seminal reducing 

 power and the bulk of the reducing material was found to consist 

 or ergothioneine, a substance which owes its reducing power to a 

 sulphydryl group (Leone and Mann, 1951; Mann and Leone, 1953). 

 The properties and functions of ergothioneine will be discussed 

 later (p. 174). 



