to the law of heredity in its every organ and tissue, it 

 assuredly follows that what is true physiologically and 

 psychologically, must, as a natural sequence, be true also 

 pathologically. We are prone to talk of the constitution 

 of an individual. What do we mean by the term, and what 

 does it involve ? A sound constitution has been defined as 

 the harmonious development and maintenance of the 

 tissues and organs of which the body is made up. Whence 

 does it originate? From the union of a healthy sperm 

 and germ cell in the maternal womb. To this same union 

 I have already traced the source of heredity : so that every 

 constitution has its foundation laid, and its deficiencies 

 and potentialities developed and maintained in accordance 

 with the law of heredity, to which they are alike subject 

 from the time a germinal vesicle is produced by the fusion 

 of the germ with the sperm cell. Irrespective of the 

 definite inherited forms of disease which contribute to consti- 

 tutional unsoundness, the latter condition may also be the 

 result of defective or deficient vitality, which may be general 

 or local. When general, this deficient vitality is frequently 

 observed in " the children of parents one or both of whom 

 are in advanced life, or whose vitality on one side or the 

 other has been reduced by excesses, such as alcoholic or 

 venereal. Exhausted vitality from prolonged disease, e.g., 

 phthisis or tertiary syphilis, affecting either parent, may 

 determine the death of the offspring at an early period 

 from mere failure of nutrition, or may cause it to succumb 

 to acute disease not necessarily associated with any inherited 

 tendency of a special kind." Deficient vitality may also be 

 local, i.e., affecting only certain tissues and organs, or 

 involving certain systems, as the nervous, the respiratory, 

 the vascular, generative, or digestive ; and amongst those 



