WHAT IS A DISEASE? 1 



By CHARLES MERCIER, M.D., F.R.C.P., F.R.C.S. 



The next question to determine is whether structural damage 

 is necessary to the concept of disease. Do we, when we think 

 of a disease, necessarily mean structural damage with its 

 consequences, or may there be diseases in which no structural 

 damage is known ? Unquestionably there may. In many of 

 the diseases, nay, in most of the diseases, considered as such 

 by our forefathers, no structural damage formed part of the 

 concept, or was known to exist. When cough, syncope, 

 hsemoptysis, haematemesis, haematuria, albuminuria, were 

 reckoned as diseases, they had no structural basis. In our 

 own time, paralysis agitans and diabetes were known as diseases, 

 though they had no known structural basis. It is true that 

 in these cases, though no structural basis was known, yet it 

 was assumed that there was a structural basis, and it was 

 confidently anticipated that this structural basis would even- 

 tually be found ; so that it may be contended that some struc- 

 tural basis, even if only conjectural or postulated, entered 

 into our concept of these diseases ; but this is not so, for there 

 are some diseases, to which every one would allow the title, 

 in which no basis of structural damage is suspected, and in 

 which we feel confident that no such basis exists. In hysteria, 

 for instance, in blindness and deafness from shock, in some 

 cases of epilepsy, in some cases of insanity, we can affirm 

 with confidence that no structural basis underlies the disease ; 

 and yet these are undoubtedly and indisputably diseases. 



Although, therefore, in many cases the structural basis of 

 the symptoms does enter into our concept of the disease, yet 

 in others a structural basis forms no part of the concept ; and 

 in these cases nothing is left but symptoms. The symptom 

 or symptoms then constitute the disease, and we are once 

 more confronted with the problem of what it is in our way of 

 contemplating a symptom or a group of symptoms that con- 



1 Continued from Science Progress, October 1916. 

 410 



