2 3 6 



health and disease, both of which I contend, in diseases as 

 in health, are essentially subject to the law of heredity. 



In considering what is meant by predisposition, I dis- 

 cussed it under the following heads viz., hereditary, aetal, 

 sexual, and acquired, and showed that it consisted in a 

 peculiar state of the physical and mental constitution of 

 every individual, mainly hereditary, which renders him 

 specially liable to suffer injuriously from the effects of cer- 

 tain morbific agents, and when these latter are of a non- 

 specific type, predisposition will determine the particular 

 disease which it shall induce in each of several individuals 

 similarly exposed to it : whilst in the case of a specific agent 

 or morbid poison, it determines the relative liability of 

 several individuals similarly exposed to it, to become the 

 subject of the particular diseases it is capable of originating, 

 and also influences the severity of its attack. 1 In other 

 words, just as every individual differs from every other 

 physiologically and psychologically, so he differs from every 

 other in his predisposition to disease, and all these differ- 

 ences are the result of heredity and variability. Predis- 

 positon is, in fact, a tendency, mainly hereditary, in the 

 tissues or organs of the body to readily assume certain 

 morbid processes, in the presence of certain exciting causes, 

 and may thus be regarded as the result of a minor degree 

 of heredity to that in which certain morbid conditions are 

 actually transmitted. There is probably no individual in 

 existence who has not inherited some predispositions to 

 disease, and we thus see that heredity and variability 

 influence man physiologically, pyschologically, and patho- 

 logically, in fact, as in health, so also in disease. Instead of 

 a predisposition, it may be an insusceptibility to certain 

 1 Dr. W. B. Carpenter. 



