198 



GROWTH 



PRINCIPLES AND THEORY 



0.5 



tal 

 ta5 



ta2 



ta3 



ta4 



Fig. 17. Length growth of the tarsi of Blatta orientalis (S. Semilogarithmic plot showing ex- 

 ponential growth decreasing with attainment of the adult state; abscissa indicates the 

 successive moltings. a First leg: hip (A), femur {fe), tibia {tb), trochanter {tr), tarsus {to); 

 b first tarsus: ^Aj etc., the consecutive segments. After Voy 1951. 



Third type. While terrestrial pulmonate snails show weight- dependence of meta- 

 bolic rate and exponential growth, fresh-water pulmonates represent a third type 

 where metabolic rate is intermediate between surface and weight proportionality. 

 Inserting a value 2/3 < m < i into equation (5.18), it follows that growth should 

 obey a third type. The curve of weight growth does not differ much from the 

 first type, but the curve of linear growth is characteristic, being sigmoid with an 

 inflexion. This prediction also is verified (Fig. 18). 



So in diflferent animal classes there are different metabolic types and different 

 types of growth, agreeing with theoretical expectation. Table 6 (p. 180) gives a 

 survey of examples investigated, and may be considered as a first draft for a new 

 chapter in physiology, namely, a comparative physiology of growth. The growth type of 

 an animal can thus he predicted {rom its metabolic type. This prediction has proved 

 to be correct in a large number of cases, often in an unexpected way. 



(7 ) Verification of the constants of the growth equation 



In well-analyzed cases, the constants of anabolism and catabolism calculated 

 from the growth curve can be verified in physiological experiment. This is of 

 decisive importance for the theory as it shows that the formulas applied are not 

 solely descriptive of empirical data but reproduce the physiological basis of growth. 



With regard to the anabolic constants (75) it follows from theory that the ratio 



