REGENERATION AND DEATH 185 



calculated the sizes of nuclei. His observations were 

 on the liver and pancreas of white mice. The figures 



New born Half grown Full grown 



Liver 5.9 n 6.2 jj. 8.2 n 



Pancreas 5.06 n 5.75 n 



in the table give the average diameters, based in each 

 case on the measurement of fifty nuclei. Professor 

 Hertwig, in the article just referred to, has demon- 

 strated that for each kind of cell there is a characteristic 

 proportion between the nucleus and the protoplasm, 

 so that large cells have large nuclei, and small cells 

 have small nuclei. This conception is certainly most 

 valuable, and if we make the necessary allowance for 

 the change in proportion during cytomorphosis, it 

 seems to be fully justified by the facts. And again, 

 we know that the nucleus provides certain chemical 

 supplies for the life and functioning of the cells. This 

 is very strikingly the case, for instance, in regard to 

 the cells which secrete. These, when they give off 

 the material which they have accumulated in their pro- 

 toplasm as a preparation for the act of secretion, are 

 found not only to reduce the bulk of their protoplas- 

 mic bodies, but the bulk of the nuclei as well. And 

 we know again that the size of nuclei may be changed 

 by somatic conditions, by food supply, so that in every 

 generalisation reached by the study of the size of 



Anatomische Anzeiger, xxxi., 306-311 (1907). It is singular that the author has 

 not reduced his measurements so as to give the absolute dimensions of the 

 nuclei. By supplying this omission I have obtained the values given in the 

 main text. 



