Chemical and Physical Properties of Semen 37 



fraction comprises 5-20%, the sperm-rich fraction 30-50%, and the 

 post-sperm fraction 40-60% of the total ejaculate. The pre-sperm 

 fraction which is ejaculated first, consists of a watery, often dis- 

 coloured, more or less sperm-free secretion, probably of urethral 



12 3 4 5 6Min. 



Fig. 7. Composition of boar semen fractions collected by the 'split-ejaculate 

 method* at half-a-minute intervals. 



A, sperm number xlO^/fraction (• #); B, fructose content, 



mg./fraction (O O); C, ergothioneine content, m./fraction 



(• •). 



(Glover & Mann, 1954) 



