8 CHARLES R. STOCKARD 



Lang was in no sense an experiment aimed towards the in- 

 vestigation of the problems we are now discussing. So far 

 as our knowledge goes, the present study is the initial at- 

 tempt on anything like a sufficiently large scale to analyze 

 the structural qualities of the dog breeds on the basis of their 

 hereditary constitutions and their endocrine conditions. It 

 should be clearly understood that our aim is to give an 

 experimental analysis of constitution in a comprehensive man- 

 ner and not simply to report on the genetics of isolated 

 characters among dogs. A preliminary consideration of the 

 general significance of these problems was given after a 

 survey of the histological conditions of the glands in numerous 

 breeds, and the earlier results of the hybridization experi- 

 ments were considered in several chapters of my book on 

 personality ('31). 



The purpose of this report is to present the results of an 

 extensive series of new experiments and to discuss the in- 

 vestigations as a connected whole, since the various problems 

 concerned are so closely interrelated that they cannot be 

 fairly considered or properly analyzed in any other way. 

 The considerations must involve the inheritance and develop- 

 ment of the finished type, both from the morphologic and 

 functional standpoints. We fully recognize that much is 

 lacking at present in our knowledge of the chemistry of the 

 functional side. Most of the phases, as would be expected 

 in so large a problem, are still in their early stages, and we 

 appreciate quite fully that this investigation has extensive 

 boundaries, the thorough survey of which is a future accom- 

 plishment. Nevertheless, we believe that the present attack 

 outlines a logical and productive means of approach, and 

 that the evidence presented in this contribution analyzes to 

 some extent the significance of the genetic constitution in 

 determining developmental and growth reactions of bodily 

 tissues and parts in their responses to different internal 

 chemical or endocrine environments. Numerous results of 

 the functional modifications which accompany definite struc- 

 tural and glandular deviations from the normal type are also 



