INTKODUCTION 27 



no striking delay of puberty among the Negroes. In fact, the darker 

 races tend to mature earlier than the light. 



The theory that the human types are determined by endocrin factors 

 has been pushed by certain writers of late years much further than indi- 

 cated in the preceding paragraphs. Pende, for example, lays great stress 

 on "endocrinopathic constitutions" as determining not only structural 

 characteristics but also liability to endocrin and other diseases. That 

 there is a fairly well marked "status thymolymphaticus" cannot be ques- 

 tioned. That the various endocrin glands may, by their inherent or 

 acquired tendencies to over- or under-activity, materially modify the 

 "constitution" is not intrinsically improbable. There is not, however, 

 in the opinion of the writer, sufficient clean-cut evidence available upon the 

 point to permit any very valuable generalizations. 



While it seems a priori likely that variations in endocrin predomi- 

 nance or deficiency may lead to marked alterations in body structure of 

 sufficient magnitude to serve as racial criteria, there is no theoretical 

 necessity for assuming such factors, or indeed not any great philosophical 

 gratification in so doing. In many instances we are perforce reduced to 

 vague conceptions of precedent variations in germ plasm to explain somatic 

 differences. That the sealion develops flappers, for instance, whereas the 

 fowl develops wings and the dog legs, can scarcely be ascribed to the action 

 of hormone factors, at least in the ordinary sense of the term. Similarly, 

 the determinants of racial stature may also reside in the germ plasm, and 

 this come to light in postpuberal development as a manifestation of in- 

 herent growth tendencies. Whether hormone determinants actually are 

 involved in development of racial characteristics remains for future re- 

 search to disclose. A first step towards a solution of the problem would 

 be to make a careful study in the various races of the endocrin organs 

 from infancy to early postpuberal life, determining both their relative 

 weights and relative degree of secretory activity, and particularly de- 

 termining whether endocrin activity precedes or accompanies the appear- 

 ance of the characteristics ascribed to it. So far as the writer is aware, 

 no significant data along this line have been secured. 



Methods of Investigation of Endocrin Functions 



Two general types of investigation have been widely utilized in the 

 study of the functions of the endocrin organs, namely, augmenting and 

 decreasing by various methods the function in question. In frequent 

 instances a sequence of the two methods, one being used as a check on the 

 others, has yielded important data. 



Several different methods of increasing the hormone content of the 

 blood have been employed, such as administration of extracts or organ 



