GENETIC TYPE AND THE ENDOCRINES 23 



and type strongly suggesting the giant mutants among mam- 

 mals. 



Most remarkable of all deviations from normal stem size 

 have occurred among the fossil and modern reptiles. Giant 

 reptiles attained an exaggeration in size during the Triassic 

 period which surpasses the performance of modern mammals. 

 The mutations giving rise to these enormous individuals 

 might be imagined to have produced a pituitary reaction in 

 the total glandular complex that was par excellence the acro- 

 megalic giant combination. 



The living reptiles still present clear examples of exag- 

 gerated types. The giant crocodile and alligator, as well as 

 some giant lizards, show an excessive overgrowth of loose 

 wrinkled skin along with other acromegalic symptoms. It is 

 also important that many of these animals do not attain a 

 limited adult size but continue to grow throughout their lives. 

 Their reproductive functions do not cease with age and they 

 show none of the usual symptoms of senility. The nature 

 of the pituitary function in these animals is entirely unknown. 



There are, at the other end of the reptilian size scale, tiny 

 active midget lizards with definite uniformity of body size, 

 and also sluggish achondroplasic bulldog-like lizards of the 

 "horned toad" type. Whether or not modified growths and 

 varieties of form are primarily caused by changes in endo- 

 crine secretion, there is the peculiar fact that such reactions, 

 in mammals at least, are almost constantly associated or 

 correlated with definite glandular peculiarities. 



The fact that the above forms are clearly recognized animal 

 species does not preclude definite comparisons of their size 

 and type with those of the newly established dog breeds or 

 with the unusual growth modifications which occur among 

 human beings. Much evidence is accumulating to indicate 

 that nature brings about growth deviations from a stem 

 pattern in closely similar ways among widely different species. 

 We have considerable justification for considering the achon- 

 droplasic reactions shown by man, dogs and cattle to be of 

 the same nature and origin as "parrot head" and shortened 



