8 4 



and involve no tendency to disease, the diatheses, on the 

 other hand, are purely pathological, and consist essentially 

 of a morbid proclivity. Thus the last three diatheses 

 mentioned in this classification should be relegated to the 

 temperaments, as they concern only the physiological differ- 

 ences between man and man, and do not necessarily imply 

 any predisposition to disease. 



It may be here mentioned that whilst we regard a diathesis 

 as a constitution of body which, in the course of life, at 

 various periods, and under varying circumstances, will give 

 rise to local or general diseases, characterised by a common 

 resemblance, either as to their etiology, . symptoms, or 

 pathology, and thus constituting a unity, yet the various 

 diatheses, owing to the action and interaction of heredity 

 and environment, combine with each other in various 

 degrees, and thus result in complex or composite diathetic 

 varieties. For like heredity, without evolution, if the 

 diatheses were transmitted without variability, they would be 

 indefinitely inherited with the same specific characters, which 

 we know would not be in consonance with natural law. 

 And thus, in practice, every day of our lives, we meet with 

 patients who, while they afford us typical examples of this or 

 that diathesis, yet reveal the elements of others in various 

 degrees. As the so-called laws of Nature represent merely 

 the grouping of certain phenomena, so diathesis may be 

 regarded as the grouping of certain constitutional pecu- 

 liarities, having certain pathological tendencies, in certain 

 families or individuals ; and, as every individual differs from 

 every other, in every respect, we must naturally be prepared 

 to admit a similar differentiation with regard to his diathetic 

 peculiarities. Diatheses are, in fact, but rough types of 

 constitutional peculiarities, showing a predisposition to 



