Chapter 1$ 

 Individuality Differentials and Blood Groups 



Towards the end of the last century and in the beginning of this, 

 serological methods had been established which made possible the 

 distinction of species and wider groups of organisms. It was natural 

 that the question should have been raised as to whether it might not be possible 

 to distinguish races and even individuals belonging to the same species by 

 these means. Thus Bruck believed that by the use of the complement fixation 

 method it was possible to distinguish between different human races. Land- 

 steiner, in order to find individual differences, studied the interaction of 

 blood serum and erythrocytes in man and thus discovered the existence of 

 four primary blood groups, which are based on the possession or lack of 

 possession of the agglutinogens A and B in the red blood corpuscles and of 

 specific agglutinins for the four types of erythrocytes. Subsequently it was 

 found that also certain animal species possess similar blood groups and that 

 there may even be an identity of some of these antigenic factors in the eryth- 

 rocytes of different species, as for instance, of man and certain apes. A 

 comparison of the distribution of these blood groups in different human 

 races showed that the proportions of the four blood groups differed in differ- 

 ent races, but that the blood groups which did occur were always the same. 

 It was furthermore established that the interaction between the agglutinins 

 in the blood plasma or serum and the blood-group factors is responsible for 

 thrombi which form in the blood if blood transfusions are made in case the 

 donor and recipient belonged to different blood groups. There was a definite 

 analogy between the blood, with its cells and the complex protein-containing 

 medium surrounding these cells, and a tissue in which the cells were sep- 

 arated by intercellular substances. 



Previous to the serological investigations which led to these discoveries, 

 surgeons had noticed a difference in the results of tissue grafting, in par- 

 ticular of skin grafting, if the latter was made into the person from whom 

 the skin flap was taken, or into other individuals, and this observation sug- 

 gested the presence of chemical differences in the constitution of these tissues 

 in different individuals. Similar differences were found in experimental trans- 

 plantations in animals and also, as we observed, in the transplantations of 

 tumors; we interpreted these differences as being due to the specific bio- 

 chemical relationships between the bodyfluids and the tissues in donors and 

 hosts. In continuation of this work, begun in 1909, finer methods were de- 

 veloped for the investigation of the relationship between such tissues. These 

 depended largely upon the study of the cellular interactions between tissues of 

 the host and of transplants. On the basis of these investigations, gradually the 

 theory of the individuality differentials developed, according to which all 



150 



