HORMONE FACTORS IN GROWTH AND DEVELOPMENT 193 



Even in the same individual the effect is different in different develop- 

 mental stages. According to Robertson the anterior lobe substance when 

 fed to mice exercises an accelerating effect upon growth only during cer- 

 tain periods of life, while in other periods growth may be even retarded ; 

 in the latter case the organism develops, as Robertson thinks, a compensa- 

 tory mechanism and through the action of this mechanism, which persists 

 even after the discontinuation of the hypophysis diet, abnormally large 

 animals may be produced, if the hypophysis diet is discontinued at the 

 proper period of growth. Similarly in the hypophysis fed larvae of frogs 

 Hoskins and Hoskins (c) found a retardation of growth in very young 

 stages, which was sometimes so great that these larvse remained perma- 

 nently smaller than the controls, although larvse treated with hypophysis at 

 a more advanced stage grew larger than the controls. A retardation of 

 growth in early stages was also found by Wulzen (a) and by Winternitz in 

 hopophysis-fed chicks. Uhlenhuth saw neither an acceleration nor a 

 retardation during the larval period of the tiger salamander, while after 

 metamorphosis an enormously increased rate of growth resulted, if the 

 hypophysis diet was continued. While in these cases no definite explana- 

 tion is possible, some insight was recently gained into the causes which 

 determine whether hyperpituitarism leads to gigantism or to acromegaly ; 

 it is now a generally accepted view supported especially by Gushing and 

 his collaborators (but opposed by Falta) that hyperthyroidism leads to 

 harmonious overgrowth of the entire body if it starts in young persons 

 whose epiphyses are still open, while initiation of hyperpituitarism after 

 the fusion of the epiphyses produces disproportionate growth of only the 

 acra. 



It is of considerable importance as regards the final result of anterior 

 lobe administration whether or not the individual is in the possession of 

 a normally functioning hypophysis; Smith (c) found that while normal 

 tadpoles react with increased growth upon anterior lobe feeding, hypophy- 

 sectomized tadpoles are able to utilize the hormone to a still greater extent 

 and consequently their growth surpasses that of the normal hypophysis-fed 

 animals. Well in accord with this experience is the important discovery 

 made by Gushing that injection of anterior lobe extract, while it produces 

 no effect in normal individuals, causes a rise in temperature of from 

 2 to 4 C. in hypophysectomized mammals; very likely both of these 

 phenomena are brought about by the same mechanism. 



Another noteworthy observation is that not all parts of the same 

 organism react quantitatively in the same way to the anterior lobe sub- 

 stance. Hoskins and Hoskins (c), for instance, found that in tadpoles fed 

 anterior ]obe the tail grew more vigorously than the body. Uhlenhuth 

 observed that in metamorphosed salamanders fed anterior lobe the tails 

 attained such an enormous length that an entirely unproportionate ap- 

 pearance is peculiar to these animals (Fig. 1). It is, however, doubtful 



