He showed that in higher animals the decrease in the rate of growth is inversely 

 proportional to the time that has elapsed since the beginning of development. 

 According to Shmal'gauzen, the reduction of the rate of growth is the principal 

 determinant of the onset of the processes of attrition of tissues and the death of 

 the organism. 



Shmal'gauzen distinguishes four factors that determine the growth of or- 

 ganisms: a) the growth (increase in the mass) of the cells; b) the growth of un- 

 differentiated tissues as a result of the multiplication of cells; c) the growth of 

 differentiated cells of tissues; d) the increase in the apoplasm (metaplasm) 

 [tr.: deutoplasm?] 



He assigns a leading part in the cessation of growth and in the weakening 

 of the autoregeneration of the protoplasm to a decrease in the mass of the un- 

 difTerentiated cells in the organism. Differentiation of the cells leads to a cessa- 

 tion of their growth, which is as exponential in the early period of embryogenesis 

 as it is in some bacterial cultures. In embryos "in the period of intense growth, 

 the phenomena of differentiation are in the background, while during the period 

 of intense differentiation growth is inhibited" (I. I. Shmal'gauzen, 1936). 



In the multicellular organism, the age-associated lowering of the growth 

 rate is determined largely by the decrease in the mass of the undifferentiated 

 tissue elements. Undifferentiated cells continue to grow as rapidly (with the 

 same growth constant) as in early ontogenesis. Hence, "the relative mass of 

 indifferent cells with exponential growth decreases in inverse proportion to its 

 age. We have here, to be sure, the entire substance of our growth law, which 

 could be designated, with equal success, as the law of gradual differentiation 

 of the organism" (I. I. Shmal'gauzen, 1936). 



On the basis of this concept of the mechanisms of growth and its relation- 

 ship to differentiation, Shmal'gauzen developed his theory of aging. One of 

 the fundamentals of this theory is a recognition of the fact that aging and death 

 are regarded as the result of the increasing differentiation of the tissues (cells). 



In addition to this, and contrary to the view of M. S. Mil'man, 

 Shmal'gauzen must be aware that specialization of cells not only increases their 

 functional capabilities but also increases their life span (vital stability) substan- 

 tially, as well as the integral system of the organism. "Specialization of the 

 somatic cells of higher animals is connected with a more nearly perfect accom- 

 plishment of certain fixed functions, and in the exact coordination of the activity 

 of the individual cells and various organs of a complex organism it assures the 

 best conditions for their existence and we should not be surprised, therefore, 

 that this specialization leads to a considerable increase in the life span of the 

 individual cells. In higher animals, this life span of the more specialized and 

 therefore unchanging cells (such as those of the nervous system, for example) is 

 determined by the life of the whole individual i.e., it is measured in years, 

 decades, and even centuries. The stability of the somatic cells has been in- 

 creased considerably as a result of their specialization, and the most stable of 

 these are always the most specialized nerve and muscle cells" (I. I. 

 Shmal'gauzen, 1926). 



26 



