1914] Lafayette B. Mendel 157 



was a place where one could work incessantly without the necessity 

 of preparing one's results for publication. ) 



It is surprising that in comparison with other topics of physio- 

 logical study so little has been published in the past about growth ; 

 and much of what has been written invades the domain of hypoth- 

 esis and speculation. Together with inheritance, growth provides 

 for the permanence of the various external manifestations of hfe. 

 The Problems of agriculture — the production of the plant products 

 from the soil and animal husbandry — are based upon considerations 

 of growth. I need scarcely add that it would be of immense direct 

 importance to man and to medicine to know more about " the regu- 

 latory power which presides over growth," so that we might derive 

 more practical applications of the discoveries in this field. In ulti- 

 mate analysis all of our material prosperity, indeed, the very pos- 

 sibility of the maintenance of the race, depends upon the manifesta- 

 tion of growth. 



The dominating viewpoint in the consideration of the phe- 

 nomena of growth will be determined in large degree by the train- 

 ing and immediate interest of those engaged in the analysis thereof. 

 Some investigators — and these represent by far the largest group 

 — have directed their attention to the purely morphological aspects 

 of the subject. Cytological phenomena, the changes in the number 

 and size of the body cells, the interrelation of the tissue components, 

 the comparative proportions of nucleus and cytoplasm, and similar 

 structural differentiations have engrossed their interest. Others, 

 again, have encompassed the problems of growth from what may 

 be called a dynainic Standpoint. By these, developmental processes 

 are looked upon as expressions of changes in equilibrium. Chemical 

 and physico-chemical reactions are brought into play. The language 

 of a chemist is exemplified in the contention that growth appears to 

 be "the expression of autocatalytic chemical reaction," and par- 

 ticular cycles of growth of an organism are accordingly shown to 

 obey a precise mathematical formula. Somewhat more tangible 

 than the distinctly hypothetical analyses of the chemical character 

 of life phenomena and the physical structure of living matter are the 

 conceptions of those scientists who aim to correlate growth with 

 nutrition, emphasizing in some cases the material side and express- 

 ing the relationships in units of matter, or in others combining with 



