INTRODUCTION 25 



individuality, of the contrast between mosaic and essential individuality, of the 

 phylogenetic and ontogenetic development of the organismal and, in particu- 

 lar, of the individuality differentials which we have mentioned in the first part 

 of this chapter, and which will be discussed in greater detail in the following 

 chapters. 



At first various fields of investigations relating to the biological basis of 

 individuality, which have been enumerated in the preceding discussion, de- 

 veloped separately, but gradually an interaction between these diverse lines 

 of investigations was established and proved fertile. In the beginning of this 

 century it was mainly the concepts of immunology which greatly influenced 

 the study of the transplantation of tissues, but later a reciprocal influence be- 

 came noticeable and during the last fifteen years the analysis of individuality 

 by the method of transplantation has stimulated also the search for individ- 

 uality differentials in various antigens by immunological methods. 



In the studies mentioned so far, the question of individuality and specificity 

 was considered from purely theoretical points of view. But the requirements 

 of social life and especially also the need to sustain the health of body and 

 mind of the individual members of a community and the harmonious relations 

 between those that compose a social group, made it necessary to face the 

 problem of individuality from a somewhat different viewpoint. This has led 

 to the concept of "constitution" as something which is peculiar to individuals 

 and allows the classification of certain groups of individuals according to 

 their reactions to various environmental conditions. It was observed that dif- 

 ferent individuals behaved differently in the same environment and under ap- 

 parently identical conditions. On this basis a distinction was made between 

 the environmental factors and the substratum on which the latter act. The 

 mode in which the substratum responded to conditions in the outer and also in 

 the inner environment, depended on and revealed the constitution of this sub- 

 stratum. While various characteristic features of a constitutional nature were 

 shared by a number of individuals, in the totality of these features each in- 

 dividual was unique and differed from every other one; and it was especially 

 the physician for whom these individual- and group-constitutional differences 

 were of practical importance. Thus the concept "constitution" developed in 

 response to the needs of daily life, and it accentuated, as does also the concept 

 "individual," the contrast between the organism and the outer world. The 

 analysis of constitution is therefore another step in the delineation of in- 

 dividuality and personality from the surrounding world. It is an attempt to 

 determine what in our interaction with the living and non-living world around 

 us is due to ourselves and what is due to the world outside ourselves. But here 

 great difficulties arise because of the great complexity which exists in the 

 interaction between the individual and the outer world, and between the outer 

 and inner milieu of a higher organism. 



However, through experiment and observation it has been learned that 

 certain characteristics of an organism are fixed in the germ cells and give rise 

 to certain structural, metabolic and functional conditions in the individual. 

 These inherited features represent the core of his constitution; it is the un- 

 changeable part of it. But in actual life it is often very difficult or impossible 



