i 7 8 AGE, GROWTH, AND DEATH 



seen so many examples in the previous lectures. 

 You will recall that as regards the size of cells, the 

 nerve cells present a noteworthy exception in that they 

 differ according to the size of the animal ; and their 

 nuclei differ also, for as the cells become big the nu- 

 clei grow likewise. Here are nerve-cell nuclei, loand 

 1 1, in the rabbit of twelve and one half days, not dif- 

 fering in their dimensions essentially from the nuclei 

 of other types, but in the two lower figures, 22 and 

 23, we see nuclei of corresponding cells of the rabbit 

 at sixteen and one half days. These cells have begun 

 to enlarge, to assume the greater dimensions of the 

 nerve cells which are characteristic of the rabbit when 

 adult ; and accompanying the enlargement of the cells 

 there has been an expansion of the nuclei also. But 

 this does not affect, as you will readily see by the 

 pictures upon the screen, the nuclei of any other sort 

 of tissue, the nuclei of any other organ of the body. 



The differentiation of nuclei has been little studied. 

 We have the valuable observations of Eycleshymer 

 on the nuclei of muscles, which I have already cited. I 

 know of no other exact work except in regard to the 

 nuclei of nerve cells, the genetic changes in which have 

 been recently studied with care by Bombici, Olmer, 

 Hatai, Marinesco, Lache, and Remy Collin. 1 The paper 



1 Bombici, " Sui caratteri morfologici della cellula nervosa durante le 

 sviluppo. Osservazioni eseguite sull* embrione di polio," Archivio Sci. 

 Mediche, xxiii., 101-125 (1899). 



D. Olmer, " Quelques points concernant 1'histogenese de la cellule nerveuse," 

 C. R. Soc. Biologic, Paris, 1899, pp. 908-911. 



Shinkishi Hatai, " A Note on the Significance of the Form and Contents of 



