206 AGE, GROWTH, AND DEATH 



power of cells kept more or less in the young type, 

 which for some reason have got beyond the control 

 of the inhibitory force, the regulatory power which 

 ordinarily keeps them in. No picture of the growth 

 or development of the living animal would be com- 

 plete if it confined its attention only to the power of 

 growth in relation to cytomorphosis. It must also in- 

 clude the contemplation and study of the regulatory 

 power of the organs. Experiments are being made in 

 many places, minds are at work in many laboratories 

 upon this problem of the regulation of structure and 

 growth. Much is to be hoped from such researches; 

 not merely insight into the normal development, but 

 insight also into the abnormal. Nothing, perhaps, is 

 more to be desired at the present time than that we 

 should solve the mystery of the regulatory power which 

 presides over growth. It would be of immense medical 

 importance. Could we understand it, and could we 

 from our understanding derive some practical applica- 

 tion of our scientific discoveries in this field, in other 

 words, could we learn to regulate the formation and 

 growth of tumors, we should say of it justly that it 

 was as noteworthy a contribution to medical know- 

 ledge as the discovery of the germs of disease, and 

 would doubtless prove equally beneficial to mankind. 

 Although, then, the /tudy which I have been laying 

 before you must necessarily seem in many respects 

 abstruse and far away from practical applications, we 

 learn that it is not really so, and that it leads by no 

 very remote path to the consideration of problems 



