6 The Biochemistry of Semen 



yields on hydrolysis glucose (as determined by glucose oxidase) 

 seldom exceeds 01%, and may be as little as 0019% (Mann, \9A6b). 

 Similarly, in sea-urchin sperm {Echinus esculentus), the ethanol- 

 precipitable, glycogen-like material separated from sperm and 

 analysed after acid hydrolysis by means of glucose oxidase, repre- 

 sents no more than 004% on a wet-weight basis (Rothschild and 

 Mann, 1950). Even oysters, in which as much as one-third of the dry 

 body weight may consist of glycogen, produce spermatozoa which 

 when ripe, contain no more than 1 % glycogen on a dry-weight basis 

 (Humphrey, 1950). 



Yet another phenomenon accompanying spermatogenesis is a 

 significant change in the distribution of lipids. In the deer (Wislocki, 

 1949) and in the rat (Lynch and Scott, 1951), sudanophilic material 

 is concentrated chiefly in the Sertoli cells, but in man (Montagna, 

 1952) a high content of lipids is characteristic alike of the Sertoli 

 cells as well as the cytoplasm of spermatogonia and of primary 

 spermatocytes. Similarly, in certain invertebrates, as for example, 

 Lithobius forficatiis (Monne, 1942), lipids form a highly characteristic 

 component of the cytoplasm in spermatocytes. These cytoplasmic 

 lipids are usually birefringent and give positive reactions for steroids. 

 In ejaculated spermatozoa, at any rate those of mammals, the lipids 

 are confined largely to certain definite regions such as the 'mito- 

 chondrial sheath' of the middle-piece and the so-called lipid capsule; 

 these will be described in more detail later. 



The changes initiated by spermatogenesis continue during the stay 

 of spermatozoa in the epididymis, and form a part of the 'ripening' 

 process. The metabolism of epididymal spermatozoa which are often 

 immotile, but capable of long survival, is as yet only poorly under- 

 stood. Guinea-pigs and rabbits, for example, can remain fertile 

 for some weeks after the ligation of the ductuli efferentes, and in bats 

 spermatozoa have been detected in the cauda epididymis as late as 

 seven months after the cessation of spermatogenesis. 



A striking change associated with the process of sperm ripening 

 in the epididymis is the migration of a drop-like swelling of sperm 

 cytoplasm called the 'kinoplasmic droplet' and believed to contain 

 some lipid material; when one examines spermatozoa from the caput 

 epididymidis of a mouse for example, the kinoplasmic droplet is 

 usually situated close to the proximal (anterior) end of the middle- 



