GROWTH IN TIME OF THE TOTAL ORGANISM 



189 



being an intestinal parasite, anaerobic and poikilothermic, nevertheless follows 

 the surface rule. The earthworm, on the other hand, respires through the body 

 surface, but shows weight-dependence of respiration (Mi'tUer, 1943b). 



Apparently regulatory factors, insufficiently known at present, are involved. 

 Such regulation is shown by the action of hormones in mammals. For example, 

 it is easy to induce an increase of metabolism of the entire animal by injection 

 of thyroxin in vivo; but, in spite of many efforts made, this effect could not be 

 reproduced by administration of thyroxin to an isolated tissue in vitro. On the 

 other hand, chronic hormonal changes entail changes both of basal metabolism 

 and tissue Qq , as has been shown in hypophysectomized animals and pituitary 

 dwarf mice (Bertalanffy and Estwick, 1954, cf. p. 220). Such examples show the 

 possibility of organismic factors regulating metabolic rate and at the same time 

 demonstrate that differences in metabolic rate of the entire animal may or may 

 not be reflected in the Q02 o^ isolated tissues. The most plausible interpretation 

 appears to be that with increasing body size the metabolic activity of tissues is 

 bridled, as it were, by some regulatory mechanism so that the systemic reduction 

 of weight-specific metabolic rate takes place; that the same is true of the "growth 

 potency" of tissues and organs; and that both factors are connected (Bertalanffy 

 and Pirozynski, 1953)- 



At present the metabolic type in the sense defined has to be taken as an 



200r 



100- 



80 ; 



E.60- 



40- 



20" 



30 60 100 200 300 800 



Weight in mg 



2 4 6 8 10 12 

 Time in weeks 



Fig. 8. First metabolic and growth type: Lebistes reticulatiis. a Dependence of metabolic 



rate on body size. Note the ratio of i : i^ of oxygen consumption in 9 and (5- b Growth 



curves; length growth, weight growth ((5). After Bertalanffy, 1941b. 



Literature p. 253 



