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Diathesis may be defined as a term denoting a morbid 

 proclivity existing in an individual or family in consequence of 

 his or their heredity and environment; or, still better, as "any 

 condition of prolonged peculiarity of health giving proclivity 

 to definite forms of disease." Mr. Hutchinson says : "What 

 we mean by diathesis is little other than an exceedingly 

 chronic disease. It is a disease or taint which lasts a life- 

 time, which may be active at times, and latent at times, and 

 which may be handed on to another generation." Diathesis 

 may be either inherited or acquired may be permanent or 

 transitory, or intercurrent with healthy intervals. The term, 

 strictly speaking, should never be associated with any transi- 

 tory condition of health which may pass away without leaving 

 any permanent impression upon the system, for persistency 

 to some extent is invariably implied by it. It is also 

 necessary to distinguish between the terms dyscrasia and 

 diathesis, for, whilst the former signifies actual bad health, 

 the latter simply implies a morbid proclivity which may be 

 possessed by an individual who is seemingly quite well. 



As to the causation of diatheses, it is well to remember 

 that as the health or unhealth of races, families or individuals, 

 is dependent upon transmitted tendencies, owing to the 

 action and interaction of the law of heredity in their pro- 

 genitors, and also upon the action of circumstances upon 

 themselves, the morbid peculiarities whose general pheno- 

 mena are grouped under the term diathesis, must depend 

 entirely upon the same causes. These exist hereditarily in 

 the individual, and, in the acquired form, in the circum- 

 stances of his environment the latter also accounting for 

 the development of those which have been inherited. I 

 shall now very briefly consider the classification of the 

 diatheses, or those types of morbid proclivity which dis- 



