WHAT IS A DISEASE? 419 



functional. But in the common acceptation of the terms, 

 do we mean, when we speak of organic disease, a disease in 

 which there is structural damage that could be recognised on 

 the post-mortem table or under the microscope, and by func- 

 tional disease a disease in which no such damage could be 

 found ? This I think is the distinction that most people would 

 formulate off-hand, but it is unquestionably wrong. Hysteria 

 is the very type and example of what is called a functional 

 disease, and in hysteria there are often structural changes 

 correlated with the other disorders and therefore forming part 

 of the disease. There may be wasting of muscles, shortening 

 of muscles, deformities, changes even in ligaments and bones. 

 Obviously, what is meant by a functional disease is not a 

 disease which is unaccompanied by structural changes, but 

 one in which the structural change, if present, is not correlating 

 but correlated. It is a result, not a cause, of the disease. 

 May we then describe a functional disease as a disease in which 

 there is no structural basis, in which the cause of the whole 

 combination of symptoms cannot be identified with any struc- 

 tural damage that can be found and recognised ? Many 

 would, I think, accept this as a good definition, but it is un- 

 questionably wrong, for it would include among functional 

 diseases epilepsy, chorea, neuralgia, infantile convulsions, and 

 many cases of insanity, and none of these is ever considered 

 a functional disease. Moreover, many ' organic ' diseases 

 whose correlating structural basis is now known were con- 

 sidered to be ' organic ' diseases long before their structural 

 basis was known. 



I believe that what is meant by a functional disease is a 

 disease in which not only can no correlating structural basis be 

 found, but also no correlating structural basis is believed to 

 exist. This would exclude from the class of functional diseases 

 all the diseases just mentioned,- for we undoubtedly believe 

 that in them such a basis exists, although we are unable to 

 discover it. If this is so, and if there is no structural change 

 as a correlating basis of the functional disease, what is the 

 correlating basis ? It is, or it is attributed to, the patient's 

 imagination. I do not say that ' functional ' disease is the 

 same as imaginary disease. It is not. It is clear that in 

 hysteria the contractions and other disorders of nutrition are 

 not imaginary. But what distinguishes the diseases that are 



