10 The Biochemistry of Semen 



a given ejaculate survive for the same length of time. In higher 

 mammals for instance, of the many hundreds of millions of sperm 

 cells, only a minute fraction, not more than a few thousand, reach 

 the site of fertilization, and ultimately only a single spermatozoon is 

 responsible for the fertilization of the ovum. 



Structural and chemical characteristics of the sperm-head, middle- 

 piece, and tail 



In the majority of species, including man, mature spermatozoa 

 have a filiform structure owing to the presence of a flagellate append- 

 age, although non-flagellar forms of sperm cells are not uncommon 

 in certain lower animals, for example, among Crustacea and nema- 

 todes. This peculiar filiform structure determines to a considerable 

 extent, the remarkable permeability of the sperm cell, which is per- 

 haps best illustrated by the so-called 'leakage' phenomenon, that is, 

 the remarkable ease with which even large molecules such as cyto- 

 chrome c or hyaluronidase can detach themselves from the sperm 

 structure and pass into the extracellular environment. The high 

 degree of permeability explains the speed with which exchange re- 

 actions can take place between the spermatozoa and the surrounding 

 medium, whether this be the seminal plasma or an artificial pabulum; 

 moreover it makes it possible for certain intermediary enzymic 

 reactions such as those involved in the phosphorylative breakdown 

 of carbohydrate, to be demonstrated directly in intact spermatozoa, 

 without cell disintegration which is an unavoidable prerequisite in 

 studies on the intermediary enzymes of other animal tissues. This 

 does not necessarily apply to all enzymes and the failure to demon- 

 strate an enzyme in intact sperm cells must not be taken as evidence 

 of its absence, particularly so in the case of mammalian sperma- 

 tozoa which are resistant to the action of most plasmolysing agents, 

 including water. 



The principal morphological features of spermatozoa have been 

 established largely in the last century with the help of the ordinary 

 light microscope, by pioneers such as Ballowitz, Jensen, Meves, 

 Retzius and others, but many more details have emerged since as a 

 result of the application of new techniques, particularly those of 

 histochemistry (Marza, 1930; Popa and Marza, 1931; Brachet, 1944; 

 Leblond, Clermont and Cimon, 1950; Leuchtenberger and 



