620 



REGENERATION AND GROWTH 



7 



TABLE 12 



EVIDENCE OF INCREASE IN HYDRATION IN THE EARLY STAGES OF REGENERATION 



pholipid metabolism is linked with that of nucleic acids, in growth-processes. 



The cholesterol content of regenerating liver (Tsuboi et at., 1954) and of the 

 blood (Man et al., 1946) changes little, but such small changes may be significant 

 in this precursor of important hormones. The wound-factor of certain plants 

 (English et aL, 1938) is a dicarboxylic fatty acid and lipid components are usual 

 in the plant-growth hormones (Osborne and Wain, 1951). 



The fat-soluble vitamins probably affect regeneration in animals much as they 

 do normal growth, though results to date have been conflicting (Arey, 1936; 

 Holmes, 1942). Vitamin A promotes bone-resorption during the remodellings of 

 growth (Mellanby, 1944; Fell and Mellanby, 1953) and, consequently, may 

 retard simple regeneration under experimental conditions (Barnicot, 1950). 

 Vitamin D also retards regeneration, in Anura (Rose, 1944,) and keloid-formation 

 in mammals (Marshall, 1952). Vitamin K, has been found beneficial in skin- 

 heaUng (Palladin, 1943). 



Many workers, following Morgan (1901, p. 267), have been intrigued by the 

 behaviour of a red carotinoid pigment in the regeneration of hydranths of Tubu- 

 laria (Cohen, 1952; Goldman, 1953). It is most abundant during the early stages 

 of regeneration (Goldman, 1953) and therefore may protect the regenerate, during 

 its R-phase, against photo-activated oxidation, as in photosynthesizing organisms 

 (Griffiths et al., 1955). The regeneration of many hydroids is sensitive to light. 

 The high concentration of carotenoids in ova (Goodwin, 1950) probably has much 

 the same significance as in regeneration. 



(^g) Water-metabolism 



There is an increased hydration of the tissues locally during the first stages of 

 regeneration (Table 12). This is not a passive waterlogging, through the wound, 

 in aqviatic animals (Von Levetzow, 1939) and occurs in unexposed organs and in 

 terrestrial animals. The increase is both intracellular (Johnson and Albert, 1952) 

 and intercellular (Menkin, 1950). Systemically, also, there is water-retention and 

 a considerable "ffow" of water from intact tissues, particularly the muscles (Cour- 

 tice, 1954), comparable to protein, fat and glucose flows. Increased intercellular 



