12 The Biochemistry of Semen 



latter gives no positive Feulgen reaction but stains with the Schiff 

 reagent after exposure to the oxidizing action of periodic acid as 

 demonstrated in the sperm of the hemipteran insect, Arvelius albo- 

 punctatus (Leuchtenberger and Schrader, 1950) and in bull sperm 

 (Hancock, 1952). According to McManus (1946) and Hotchkiss 

 (1948), the 'periodic acid Schiff reaction' (PAS) is due to the pre- 

 sence of carbohydrates, and the chemical groups which react with 

 fuchsin-sulphurous acid are the aldehydes formed from 1 : 2 glycol 

 groupings by oxidation with periodic acid: 

 OH OH 



I I 



R— C C— R + HIO4 -> 2R— CHO 



The acrosomal material is not glycogen as it does not react with 

 iodine and is not affected by treatment with amylase. It cannot be 

 hyaluronic acid because it resists the action of hyaluronidase. The 

 possibility that it may be related to hyaluronidase itself still remains 

 to be investigated. There has also been a tendency to regard it as a 

 mucopolysaccharide, without however, sufficient evidence. Special 

 precautions are called for in the preparation of spermatozoa for the 

 PAS reaction. Structural changes in sperm cells, such as occur for 

 example, after rapid cooling ('temperature shock'), may render the 

 acrosomal material unresponsive to the periodic acid-Schiff reagent. 

 It is not improbable that the acrosomal 'polysaccharide' is either 

 decomposed or detached from the head of a mature spermatozoon; 

 this is borne out by some microscopic observations on changes which 

 take place in the acrosome during the period of senescence and death 

 of the sperm cell. Several investigators have described in sperma- 

 tozoa yet another cap, a loose protoplasmic structure, named 'galea 

 capitis' (also 'acrosome cap', 'Kopfkappe' or 'capuchon cephalique') 

 which envelops the apical part of the sperm-head and can break 

 away spontaneously to form a so-called 'spermatic veil' or 'floating 

 cap' (Williams and Savage, 1925; Blom, 1945). However, whereas 

 most authors including Williams (1950) regard the acrosome proper 

 and the galea capitis as two distinct structural entities, some con- 

 sider them to be identical, and Hancock (1952) for instance, is con- 

 vinced that there is only one acrosomal structure and, that the de- 

 tachable cap arises through post-mortem changes, and is the result 

 of swelling and loosening of the acrosome itself. The separation of 



