The Two Components of Semen 17 



morphological structure, to be anatomically and even functionally 

 'homologous', were later shown to differ greatly in their chemical 

 secretory activity. This is particularly true of the secretions of the 

 prostate and the seminal vesicle, two organs which in the majority 

 of higher species provide the bulk of the seminal plasma; their 

 localization within the reproductive tract of several species is illus- 

 trated in Plate III and Fig. 4. 



The prostatic secretion 



This differs in many ways from other secretions of the mammalian 

 body, and its composition shows considerable species variations. 

 Much study has been devoted to the human and canine prostatic 

 fluids; both are colourless and usually slightly acid, about pH 6-5 

 (Huggins, 1947; Zagami, 1940) and both are remarkable for the 

 almost complete absence of reducing sugar. They abound, however, 

 in several strong proteolytic enzymes; the human prostatic fluid 

 contains a fibrinolysin so powerful, that 2 ml. of prostatic fluid can 

 liquefy 100 ml. clotted human blood in 18 hr. at 37°; dog prostatic 

 fluid is distinguished by its ability to destroy fibrinogen, but it is 

 relatively inactive towards clotted blood (Huggins and Neal, 1942). 

 The prostate secretes a diastase (Karassik, 1927), and a /3-glucuroni- 

 dase which is more active in man than in dog (Talalay, Fishman and 

 Huggins, 1946; Huggins, 1947). 



The prostatic secretion represents the main source of citric acid 

 and of acid phosphatase for whole human semen; and the analysis 

 of these two constituents provides a most convenient 'chemical 

 indicator test' for the assessment of the functional state of the 

 human prostate. There is much more citric acid and acid phospha- 

 tase in the human, than in the canine, secretion; thus, the citric acid 

 content is less than 30 mg./lOO ml. in dog, as against 480-2680 

 mg./lOO ml. in the human fluid; acid phosphatase activity in dog 

 corresponds to about 28 King-Armstrong units/100 ml. in the 

 'resting' or spontaneously voided prostatic secretion, and 104 

 units/100 ml. in the 'stimulated' secretion obtained by parasym- 

 pathetic stimulation, whereas the prostatic secretion of a normal 

 adult man may contain up to 3950 units/1 ml. (Gutman and 

 Gutman, 1941; Huggins, 1947). 



The concentration of osmotically-active substances in the 



