xw INTRODUCTORY LETTER TO SENATOR MOSSO 



strongly now, of getting to direct facts, I started a 

 series of observations on the growth of animals, 

 which have been continued for a long period, during 

 which the research has expanded far beyond its 

 original scope. While carrying forward my experi- 

 ments on growth, various conclusions suggested them- 

 selves ; some tentative, others more or less definite. 

 These have been partially and briefly published at 

 various times. 1 To review these publications now 

 would serve little purpose beyond possibly establish- 

 ing the claim of priority, and I will therefore merely 

 enumerate them. Moreover, in the course of the 

 following pages the more important results contained 

 in these earlier papers are brought together. My 

 experiments on growth led to a memoir 2 published 

 in 1891, in the English Journal of Physiology. It 

 dealt with the growth of guinea-pigs and is to be 

 regarded as the starting point or foundation of the 

 present work. Since then the experimental work 

 has been continued, and data concerning the growth 

 of other animals collected. They are given in the 

 course of the following pages. 



1 "Death and Individuality," Journ. Sci., vii., 72-77 (1885), reprinted, 

 Science, iv., 72-77. 



" Researches on Growth and Death," Proc. Soc. Arts (Mass. Institute Tech- 

 nol.), Meeting 310, p. 50-56. 



"The Formative Force of Organisms," Science, vi., 4-6 (1885). 



" Researches on Growth and Death and Biological Problems," Proc. Amer. 

 Assoc. Adv. Sci. for 1884, 517-521. 



"The Physical Basis of Heredity," Science, viii., 125-130 (1886). 



8 " Senescence and Rejuvenation," first paper, "On the Weight of Guinea- 

 Pigs," Journ. of Physiol., xii., 97-153, pis. I. -III. (1891), 



