WHAT IS A DISEASE? 411 



verts it or them into a disease. Is it the combination of two 

 or more symptoms ? No, for in the whilom diseases cough, 

 haematuria, palsy, dropsy, and in the present-day diseases 

 writer's cramp, wryneck, neuralgia, Dupuytren's contraction, 

 and others, there is but a single symptom ; and moreover there 

 are combinations of symptoms that do not constitute a disease. 

 A patient may suffer simultaneously from the symptoms of 

 heart-disease, ringworm, and hammer-toe, but we do not 

 regard this combination of symptoms as a disease : we regard 

 them as three different diseases. This instance throws some 

 light upon our problem. It is clear from it that whatever 

 symptoms a patient may present, they do not constitute a 

 disease unless they are correlated together ; that is to say, 

 unless they are combined by a causal nexus into a single group. 

 It may be that we can identify the tie that binds them to- 

 gether, as when we find symptoms so diverse as disorder of 

 the circulation, asthenia, vomiting, and pigmentation of cer- 

 tain areas of the skin, all associated with and dependent on 

 destructive disease of the supra-renals ; or it may be that no 

 such tie can be discovered, but yet the occurrence in different 

 persons of the same distinctive group of symptoms, or their 

 repetition from time to time in the same person, as in epilepsy, 

 satisfies us that there must be a causal tie ; but in either case, 

 we take the whole of the correlated symptoms, and mentally 

 combine them with the causal tie, and call the whole correlate 

 the disease. The correlating tie which binds the group 

 together in our minds may be structural damage of this organ 

 or that, or it may be a microbic invasion, or it may be a poison, 

 or it may be unknown, and purely conjectural ; but some 

 tie, some common intra-corporeal cause, must exist or be 

 supposed to exist before we can group the several instances 

 of disease together into an integrated whole or individual 

 thing, and call that object of contemplation a disease. By a 

 disease we mean, therefore, the whole group of correlated 

 disorders, both functional and structural, from which the 

 patient suffers; and by correlated disorders are meant all the 

 disorders that are attributed to a single intra-corporeal cause, 

 together with this cause. 



It is necessary to add the qualification ' intra-corporeal,' 

 for many diseases have a plurality of causes if we take into 

 our consideration extra-corporeal causes. Many diseases need 



