12 CHARLES E. STOCK ARD 



influence of the internal secretions, or in spite of the quality 

 of such secretions? If the latter proposition were true, the 

 bulldog head could be inherited as such with no relation to 

 the nature of the endocrine secretions as long as these were 

 sufficiently normal to permit development at all. Does the 

 genie constitution of the tissues themselves determine their 

 pattern of development in every environment sufficiently 

 favorable to permit development? Or again, to contrast these 

 propositions by concrete query, is giant growth only possible 

 from those tissues genetically constituted as giant, or may 

 the potencies for normal size be stimulated, or better, liber- 

 ated for giant growth through the action of peculiar internal 

 secretions! And finally, a combination of the alternative 

 propositions presents itself: are modified endocrine glands 

 and peculiar growth deviations correlated characters, both 

 resulting from a common genetic change, or, returning to 

 the initial question, is the one primarily and the other sec- 

 ondarily the consequence of a genetic change? Definitely 

 localized modifications of growth in the separate regions of 

 the body, as are present in some dog breeds, supply material 

 of unique value for an analysis of these questions. In fact, 

 many of the most pressing problems of constitution, develop- 

 ment and growth are subject to analysis when the array of 

 dog breeds is appreciated as peculiarly favorable material 

 for the investigation of these problems. 



Resemblances of growth deviations in man to the modified 

 forms in dog breeds. A knowledge of the dog races from 

 the biological and medical points of view impresses one with 

 the fact that many of these breeds are characterized by 

 peculiarities of type and structural modifications comparable 

 in close detail to certain unusual and so-called pathologic 

 conditions found among other mammals, particularly in human 

 families. The human giant, for example, may be a well pro- 

 portioned, overgrown individual, in type and form entirely 

 comparable to the giant Irish wolfhound or the great Dane 

 dog. In addition to these well proportioned giants are others 

 showing an excessive heaviness of skin and facial features 



