222 KERATIN AND KERATINIZATION 



1951). Both materials increase during the growing phase and decrease 

 during rest. Metachromatic staining usually indicates acid muco- 

 polysaccharides and is common in growing mesenchymal tissues else- 

 where but its exact role is not clear. Sylven's suggestion that the sul- 

 phur of polysaccharide was transferred to the growing hair through the 

 papilla and was a source of sulphur for keratinization seems to be refuted 

 by Ryder's observations to be described later (p. 232). 



Phosphatases (Fig. 97 (a)) 



Moog (1946) has summarized the evidence to show that there is 

 commonly an association between alkaline phosphatase and transport of 

 materials. The distribution of these enzymes in the skin and hair follicle 

 (Fell and Danielli, 1943; Montagna, 1956) is such as to suggest that they 

 could be concerned with the transport of metabolites. They occur together 

 with the mucopolysaccharides. From their location it would seem that 

 phosphatases are not directly associated with the processes of keratinization 

 itself. See also Braun-Falco (1958). 



Lipids (not Illustrated) 



According to Montagna (1956) lipids stainable by means of Sudan dyes 

 are not strongly developed in the lower follicle and even less can be 

 demonstrated in the upper levels. This is in contrast to the epidermis, but 

 it seems to show that lipids in themselves have little to do with keratiniz- 

 ation at least in the hard keratins. In the epidermis also they are probably 

 accessory, serving to plasticize and waterproof the formation. Contrary 

 opinions have been expressed (see Rothman, 1954). 



Water content 



The water content of the cells of the lower bulb is probably of the order 

 of 90%; that of the keratinized hair about 30%. There is clearly a 

 considerable dehydration in the course of the formation and consolidation 

 of the fibre, but it has not been measured with any accuracy. A very 

 similar dehydration occurs in the stratum lucidum and corneum of the 

 epidermis. In the hair follicle the most marked loss of water accompanies 

 the rapid synthesis and coalescence of fibrils in the upper bulb and 

 coincides with the narrowing of the lumen and the rise in birefringence. 

 It would seem that, with the condensation of the cytoplasmic proteins into 

 compact fibrous masses, many hydrophilic end groups are either modified 

 chemically or are utilized in the formation of various bonds internal to the 

 fibrils and thus release the water molecules previously bound by them. 

 The " free " water may then leave the cells for osmotic reasons. When 

 H-bonds are broken in reduced hairs a marked swelling and hydration 

 occurs, which is probably a partial reversal of processes occurring in the 

 follicle in zones B to C. 



