BIOCHEMISTRY OF THE SEXUAL ORGANS 297 



appearance, consistency and smell. The amount of semen ejaculated 

 by dogs varies from 0*5 to 30 or 40 c.c. This depends partly on the 

 size of the animal but partly also on its general condition. The 

 amount of spermatozoa present is relatively small in proportion to 

 the liquid part of the semen. In sheep the proportion is greater but 

 the total amount ejaculated does not exceed 2 to 5 c.c. In the horse 

 the volume is on the average 50 to 100 c.c. but may sometimes 

 exceed 300 c.c. 



Slowtzoff l has made comparative analyses of the semen of man. 

 horse, and dog, which have given the following figures : 



Human semen consists, therefore, roughly of ninety per cent, 

 water and ten per cent, solids, which, on incineration, yield about 

 one per cent, of ash. About one-fourth part of the solids consists of 

 proteins, of which a nucleoprotein, traces of albumen and mucin, and 

 an albuinose-like substance have been identified. The semen of the 

 dog and horse differs in containing more water. This difference is 

 made up by the presence of a large amount of various organic 

 substances in human semen, which have not been clearly identified. 



In the ash of human semen, K, Na, Ca, Mg, P, Fe, and S have 

 been found. 



The quantitative analysis of the ash reveals a remarkably large 

 amount of calcium and phosphoric acid about twenty per cent. 

 Ca and thirty per cent. P 2 5 . In man the amount of calcium 

 excreted in one ejaculation is, therefore, about O'Ol gin., and exceeds 

 that contained in an equal quantity of lime-water. Analyses of the 

 ash of the semen of other Mammals do not appear to have been 

 made, but it is unlikely that there are any essential differences. 

 Since during the breeding season about fifty sheep are served by one 

 ram, it is evident that a profound change must take place in the 



1 Slowtzott', " Sur la Composition biochemique du Liquide spermatique," 

 Compt. Rend. 8oc. de Biol., vol. Ixxix., 1916. See also Zeitsch. f. p/iysioL Ch<'m., 

 vol. xxxv., 1902. 



10 A 



