4 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



Among the higher organisms we distinguish individuals the more readily, the 

 more varied the bodily features and the psychical reactions and the more 

 intimately we are acquainted with the peculiarities which each individual 

 possesses. In the phylogenetically higher organisms the differentiation between 

 the various parts, together with their functions, is greater, and likewise the 

 integration of the parts into one organism is more fixed and rigid. Here it is 

 evident that the individual, as a whole, is the unit in the biological and in the 

 social sense, and not the elements of which the individual is composed — the 

 cells, tissues and organs ; nor is a group of individuals, whether a family, clan, 

 nation or race, the real unit. Under natural conditions the smaller component 

 units depend upon the other constituents of the integrated individual for their 

 life and function, but the groups consist of individuals who, if necessary, are 

 able to live and function independently of the other units of the group. It is, 

 therefore, the effects which the actions and policies of the various groups 

 exert on the individual which is the ultimate test of their value. The wellbeing 

 of the group depends upon the wellbeing of the individuals of which it is com- 

 posed ; but conversely, social relationship to other individuals and a healthy 

 group life are conditions which promote the wellbeing of the individual, while 

 unfavorable social relations injure him. 



All these individual characteristics in living organisms which we have men- 

 tioned so far, are localized in certain areas of the organism, in special organs 

 or tissues, and they are either structural or functional peculiarities of the 

 latter. If we conceive of the individual as a mosaic of many tissues and organs, 

 each one functioning and metabolizing in its own peculiar way, we may con- 

 sider this mosaic of separate parts as the biological basis of individuality, in- 

 cluding the psychical characteristics ; and in order to understand individuality 

 in this sense we would have to study the peculiarities of the units composing 

 such a mosaic in each individual. Also, the nervous system and the hormone 

 system which serve as means of communication between the various parts of 

 the body, represent special organs or products of organs and are therefore 

 parts of the mosaic. They are the properties of organisms, which are analyzed 

 as to their genetic basis by means of hybridizations according to Mendelian 

 methods. 



There is, however, in addition to this mosaic basis of individuality, another 

 basis. There are properties which are not restricted to certain parts of the 

 organism, but which are common to all, or almost all, parts of the organism, 

 and which, although not visible, bind them together, make them into a unit and 

 differentiate one individual from every other individual ; also one species, 

 genus, order, class of organisms from every other species, genus, order and 

 class. There is inherent in every higher individual organism something which 

 differentiates him from every other individual, which can be discovered by 

 observing the reactions of certain cells and tissues belonging to one individual 

 towards the tissues and cells of another individual of the same species. These 

 reactions are indicative of a characteristic common to all the parts of one 

 organism, which differs from the analogous characteristic of all the parts in a 

 different organism of the same species. And not only do the cells and tissues 



