296 E. R. HOSKINS 



c. Effects of thymus feeding 340 



d. Effects of hypophysis feeding 340 



e. Effects of pineal feeding 341 



V . Conclusions 341 



VI . Literature cited 343 



I. INTRODUCTION 



The present investigation was undertaken in the hope of 

 throwing further hght upon the relations of some of the ductless 

 glands to the growth process in albino rats. During the experi- 

 ment it became evident that the growth rate in the control rats 

 was in many cases somewhat different from that which has been 

 generally described as normal, so it became necessary to include 

 incidentally the question of the normal growth rate. 



The investigation was carried on in the Anatomical Institute 

 of the University of Minnesota, under the direction of Profes- 

 sor CM. Jackson, to whom my grateful thanks are due for his 

 constant interest in the work and his many very helpful sug- 

 gestions. 



Since the ductless or endocrinous glands were first recognized 

 anatomically, various methods have been applied in investi- 

 gating their functional significance. The four most commonly 

 used, are extirpation of the glands, their transplantation, in- 

 jection of their extracts and the feeding of the glandular sub- 

 stances. 



Feeding ductless glands in order to study the effects of the 

 hyperactivity thus possibly produced has certain objections. 

 The absorption is slower than when injections are made, and the 

 danger of infection is lessened; but the substances fed may un- 

 dergo digestive changes in the alimentary tract. That the 

 active principles of the ductless glands are not necessarily de- 

 stroyed by digestion, however, is proven by abundant experi- 

 mental and clinical results (Gudernatsch '12, and Abderhalden 

 '15 especially in thyroid feeding). The feeding method was 

 selected for the present investigation. 



