26 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



to separate this core from effects produced by the environment. Therefore the 

 physician especially is forced to adopt as the definition of constitution not only 

 the genotype, the inherited part of the individual, but also those effects of the 

 environment which have modified his mode of response to environmental 

 factors in a more permanent way. But different environmental factors differ 

 greatly in their intensity and in the perpetuity of the constitutional changes 

 which they produce and in the number and imporance of the parts of the or- 

 ganism which they affect. All transitions exist in this respect and no sharp 

 line of demarcation can be found between various environmental factors. It is 

 particularly the nervous system which responds most readily to the environ- 

 ment in the mentally most plastic organism, man. Every thought and sugges- 

 tion which he has received produce an important change in his constellation 

 as far as his behavior is concerned. Constitution thus becomes identical with 

 the constellation of an organism produced by all kinds of inner and outer con- 

 ditions, which regulate future reactions; it depends upon the condition of 

 organs or organ systems and corresponds therefore to the mosaic type of in- 

 dividuality. But the term "constitution" has received a different content under 

 different circumstances ; it is not sharply defined, yet it may serve as a pro- 

 visional instrument in the analysis of the reactions of an individual. 



In the following chapters we shall discuss more fully the different aspects 

 of individuality, to which we have referred in this introductory review. In 

 the various parts of this book the following problems will be discussed : 



Part I. The transplantation of tissues in higher organisms which fur- 

 nishes the most delicate tests of individuality differentials and is the basis on 

 which further theoretical considerations have been built. 



Part II. The phylogenetic and ontogenetic development of individuality 

 and organismal differentials, from the primitive to the highest organisms 

 and from the egg to the adult state. 



Part III. Conditions suggesting or simulating the presence of individuali- 

 ty differentials which exist in certain unicellular organisms, either free- 

 living, such as certain protozoa; or representing parts of more complex 

 organisms and constituents of tissues, such as amoebocytes ; or cells inter- 

 mediate between these two types, as far as their independence is concerned, 

 namely, ova and spermatozoa. 



Part IV. The organismal differentials of tumors, which represent modi- 

 fied tissues. 



Part V . The role played by organismal differentials in the maintenance 

 of the harmony of the organism as a whole, and in the interaction of the 

 organs and tissues within the organism. 



Part VI. Immune processes in their bearing on the interpretation of 

 organismal differentials. Organismal differentials as well as organ differ- 

 entials may function as antigens and give rise to the formation of immune 

 substances. 



Part VII. The relationship between the evolution of species and organis- 

 mal differentials. 



Part VIII. The significance of individuality differentials in the psychical- 

 social field; it is here that the concept of individuality had its origin. 



