GENETIC TYPE AND THE ENDOCRINES 297 



axial skeleton and nowhere else in the body ? If so, sneh 

 distortion of growth can scarcely be due to strange endocrine 

 environment. If such localized distortions could be produced 

 in a consistent manner among these hybrids, it might be 

 possible to determine whether the genetic constitution of the 

 individual induces the growth pattern of its parts independent 

 of differences in the quality of the endocrine secretions. In 

 other words, might the modifications in the structural pattern 

 usually attributed to endocrine disturbance occur in a limited 

 body region which is necessarily in the same endochemical 

 environment as are all other organs and parts which are 

 progressing on a perfectly normal plan! 



The occurrence of achondroplasia in the domestic fowl 

 as a result of manganese deficiency, recently suggested by 

 the work of Lyons and Insko ('37), is beset by the same 

 difficulty in offering an explanation as is the endocrine ex- 

 planation in answering this problem of localized chondro- 

 dystrophic reactions. 



One of the most important questions in mammalian de- 

 velopment is : just how far are genetic modifications of the 

 endocrine glands the contributing factors in bringing about 

 typically hereditary growth deviations? A definite proposi- 

 tion may further clarify the problem: docs a disturbance of 

 the pituitary gland constitute the initial cause of acromegalic 

 gigantism, or is a mutation in the genetic complex of the 

 individual responsible for both the modification of body form 

 and size and the defective pituitary? Are diseased pituitary 

 and acromegalic growth reactions two genetically correlated 

 characteristics of the giant constitutional complex, and both 

 therefore merely symptomatic of the common cause? Gland 

 operations and injections of glandular extracts have failed 

 to furnish answers to such inquiries. 



We have made extensive studies on bulldog-bassethound 

 hybrids in an effort to solve some of these problems. Two 

 pure line bassethound bitches were each mated to two highly 

 typed well bred bulldog sires. Four litters of eight, two, 



