558 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



homoiogenous sera seemed to be preferable as carriers ; at least this was found 

 to be the case in some experiments. It may be assumed that under these 

 conditions the conjugation with the hapten made the serum so strange to the 

 receptor tissue as to prevent a chemical interaction between the receptive cells 

 and the antigen, notwithstanding the identity of the species differentials in 

 both donor and host. We have perhaps, to deal with quantitative gradations 

 in such cases, in the sense that if a substance does not usually enter into 

 combination with a certain type of cells, it has a better chance to act as an 

 efficient antigen, and only slight alterations in the chemical constitution of 

 such a substance are required for its antigenic function, whereas substances 

 similar to those which commonly come in contact with the cells cannot 

 readily act as antigens. Frequent contacts of this nature may be assumed to 

 occur between constituents of homoiogenous blood plasma and cells of spleen 

 or bone marrow, in contrast to skin cells, where such an intimate contact does 

 not usually take place. 



We have referred to the significance of an inherited predisposition in 

 idiosyncrasy. While a genetic basis may be conceded, the predisposition to 

 idiosyncrasy seems not to be of a limited nature, directed against a specific 

 agent, but rather of a more general character. According to Cooke and Van 

 der Veer, it is determined by a single dominant factor ; but until quantitative 

 gradations in the degree of predisposition have been taken into consideration, 

 the mode of inheritance in idiosyncrasy must be left undecided. 



The anaphylactic phenomena, on the other hand, which have been studied 

 mainly in animals, manifest pronounced species differences as to the readiness 

 with which anaphylactic reactions can be elicited and as to the organs and 

 tissues involved. Thus the facility with which the Arthus phenomenon can 

 be produced varies very much, and, likewise, the relative importance of blood 

 vessels and bronchi in anaphylactic conditions differs greatly in different 

 species. In the rabbit, the local reactions of anaphylaxis are very marked in 

 the skin, while the stomach responds very weakly, and the intestines not at 

 all; in the dog the order of sensitiveness is just the reverse. In such cases, 

 again, differentials are involved, which form a part of the Mendelian mosaic 

 in an organism. In the predisposition to idiosyncrasy, we have presumably 

 to deal with a character which forms a part of the mosaic constituting an 

 individual, and, as we have seen, this is to be distinguished from the individu- 

 ality differential which characterizes an individual as a whole. 



The idiosyncrasies, as far as they are known to us, concern human beings 

 and represent one of their individual characteristics. They are therefore 

 comparable to various mosaic characteristics which may serve to distinguish 

 individuals, such as skin patterns, scents, tissue malformations and electric 

 brain potentials. It is an interesting phenomenon that contact with relatively 

 simple constituents of our environments can alter the reactions of tissues 

 with which they come in contact in such a specific and individualized manner. 



