2 24 READINGS IN BIOLOGICAL SCIENCE 



ASSEMBLAGE OF CHARACTERS AND QUALITIES 



Throughout this presentation it has been evident that the essential charac- 

 ters on which the inheritance of disease depends are separately transmissible 

 units of an almost endless variety. In some few instances one such unit may 

 completely control a disease condition. But in most cases not only is the 

 disease itself only partly influenced by the inheritance but even that part 

 is controlled by a number of separately inheritable unit characters. Our 

 present knowledge fails completely in so far that in no single instance does 

 it furnish a perfect insight into the fundamental nature of even one of 

 these inheritable units. The task for the future is obviously enormous if 

 we are to gain a usable understanding of the inheritance of disease on the 

 basis of rational knowledge. We require to know for the different dis- 

 ease conditions the precise part played by the inheritance m toto; the 

 number of unit characters involved for each case, and their structural or 

 functional nature. It may well be, however, that the obstacles which inter- 

 vene between our present understanding and a much more perfect and 

 useful one are lessened by some favoring circumstances which may be 

 sketched. 



While it is considered fundamental that unit character is distinct in 

 inheritance, certain definite instances are known where diverse characters 

 are usually inherited together. This is termed linkage. Thus in hemophilia 

 (which is manifest by failure of the blood to clot, so that those aft'ected 

 are "bleeders,") the disease condition is hnked with the factors determin- 

 ing the sex. It is also true that a single unit character is sometimes known 

 to be concerned with a variety of structures or functions although the 

 author is unable to point out an example of this nature with reference to 

 any disease condition. 



From the point of view of pathology, also, there are rather clearly out- 

 lined associations between certain structural pecuUarities and disease condi- 

 tions, excluding cases previously outlined where the disease is directly 

 dependent on a particular fault of structure. There are also recognizable 

 tendencies for individuals and families to suffer from or be relatively im- 

 mune to groups of diseases. Thus the tall, thin, flat-chested type of man is 

 believed to be more liable to acquire tuberculosis. People who suffer from 

 rheumatism and gout are believed to be less liable than the average to ac- 

 quire tuberculosis. Most of these relationships are, as at present recognized, 

 of the uncertain order resting on the impressions of successive generations 

 of physicians. Yet recent approaches to the subject on the basis of careful 

 measurements, accurately recorded case histories and adequate statistical 

 analysis lend credence to the belief that there is a real and traceable set 

 of associations here which it will be worth while to develop by further 

 studies. Up to now the interest had chiefly centered on recognizing certain 



