Si ADAPTATION AND DISEASE 



biophores, they sooner or later, in the metabolic processes of 

 the cell, become dissociated and broken down. 



(ii.) On the Functional (Katabiotic) and Vegetative (Bioplastic) 

 Activities of the Cell and the Individual. — In unicellular organisms 

 the growth of the individual presents itself merely as increase 

 in size : in multicellular organisms, while there may be increase 

 in size of the component cells to a certain extent, growth is 

 brought about in the main by cell proliferation and increase in 

 the number of the component cells. But both in protozoa and 

 metazoa (and protophyta and metaphyta, if the terms be per- 

 missible) there are limits to this process. Here I would but 

 rapidly refer to what constitute these limits, namely, they are 

 conditioned by the relationship or interaction between the 

 individual and its environment. Broadly speaking, the indi- 

 vidual continues to grow until an economical mean is established 

 between the amount of food-stufis afforded by the environment 

 and the absorptive surface that the individual can present to 

 that environment. It is, as I have pointed out, 1 a false con- 

 ception to regard the multicellular organism as a colony of 

 individual cells which remain united for self-defence and mutual 

 advantage. Rather it must be recognized that where the uni- 

 cellular mass of protoplasm undergoes enlargement, the greater 

 the mass the smaller relatively becomes the surface area, and 

 this diminution proceeds in a rapidly increasing ratio, until 

 growth is arrested by the fact that the amount of food-stuffs 

 absorbed cannot keep pace with the needs of the organism. 

 Nuclear and cell division and multicellularity constitute the 

 simplest mechanism whereby the nuclear and cell surface areas 

 can be increased in a yet greater ratio, and the greatest effective 

 working of the individual obtained by decentralization. We may 

 thus regard the mass or size attained by the mature individual 

 of any species as representing the sum total of protoplasmic 

 matter of the constitution peculiar to that species which is 

 capable of existing as an entity under the particular conditions 

 of its environment, the multicellular individual acquiring its 

 greater size and more complex activities by means of nuclear, 

 followed by cell division. 



From physical considerations I thus arrived at the same view 

 as that mentioned by Whitman in America (1893) and Sedgwick 



1 Principles of Pathology, 1st ed., 1908, vol. i. p. 35. 



