INTRODUCTORY LETTER TO SENATOR MOSSOxiii 



precepts of Ludwig, to prove the existence of another 

 set of correlations between the structure of cells and 

 their function, which hitherto has been unrecognised. 

 The primary correlation of the variations in pro- 

 portions, which can be demonstrated, is with the age 

 of the organism. Accordingly, the investigation of 

 age and growth occupies a large share of the 

 volume. 



The subjects discussed in this book have received 

 in part, hitherto, relatively little attention from bio- 

 logists, hence the scientific literature dealing explicitly 

 with them is rather scanty, although there are almost 

 innumerable observations recorded in various writ- 

 ings, which have a bearing on the problems to be 

 solved. Under these circumstances I have been 

 forced, necessarily, to rely almost exclusively upon 

 my own investigation ; accordingly, the conclusions 

 have a personal character in the sense that they have 

 not yet been subjected to the critical judgment of bio- 

 logists. Nevertheless, I hope that they will commend 

 themselves to you. 



My own active interest in growth as a biological 

 problem goes back twenty-nine years, when I pub- 

 lished an article on " Growth as a Function of Cells," 1 

 followed by another, "On Certain Laws of Histo- 

 logical Differentiation." 2 These two papers, however, 

 were of a somewhat theoretical character. Feeling 

 strongly the necessity, which I should feel still more 



1 Proceedings Boston Soc. Nat. Hist., xx., 190 (1879). 



2 Ibidem, p. 201. 



