modifications effected by external circumstances ; nay, 

 more, his constitutional vigour or weakness is, originally, 

 due to the same cause ; also that he bears within him certain 

 morbid tendencies which have been transmitted to him. Is 

 it not therefore evident that the morbid conditions which 

 afflict him must be due either to nature working within him, 

 or circumstances working upon him from without ? And if 

 it is conceded that his physical nature and parts are 

 originally the result of heredity that his constitutional 

 vigour or power of resistance is originally due to the same 

 cause, and that circumstances may develop inherent weak- 

 ness of tissue or organ, I ask for' nothing more, only that 

 if certain tissues or organs in the body are predisposed to 

 disease in consequence of heredity, it should be admitted 

 that all may be, and probably are ; and if such be the case 

 in brain and lung, why not also in heart, artery, and vein ? 



Coming more closely to consider the diseases and 

 anomalies of the circulatory system, I may ask, if it is 

 admitted, as it is, that the quality of a man's bones, muscles, 

 and organs is undoubtedly inherited, why should the heart- 

 muscle and the blood-vessels be excepted? And if it is 

 proved, as it is, that certain inherent weaknesses of certain 

 organs and tissues manifest a predisposition which cir- 

 cumstances may develop into disease, why should the heart 

 and blood-vessels be exempt from inherent weaknesses 

 of structure, which may in like manner predispose them to 

 disease? Without following this argument further, there 

 can at least be no doubt that physiological functions are 

 modified by anatomical structure in health as in disease, 

 and thus the physiological functions of the circulatory 

 system will be more or less modified by the structure of 

 the heart, arteries, and veins, whether hereditary or acquired, 



