WHAT IS A DISEASE? 421 



damage, and such diseases also are certainly ' organic' In 

 a third class of diseases, such as epilepsy and neuralgia, we do 

 not know the correlating cause. It may be some chemical 

 aberration in the constitution of the tissue, or it may be some- 

 thing else ; but we are quite confident that it is not anything 

 imagined by the patient. Moreover, it is not and does not 

 begin as a mere inability or incapacity. Such a disease is 

 therefore excluded from the class of ' functional ' diseases, 

 and included among the ' organic.' 



I think that this description of a functional disease as one 

 whose correlating basis is in the imagination of the patient 

 helps us to understand why it is often so very difficult to 

 distinguish ' functional diseases ' from pretended diseases ; for 

 they have in common that their origin is mental. In the one 

 case the origin is in the imagination, but the disease is a true 

 disease, and is curable by the ministrations of the physician. 

 In the other case the origin is in the will, the disease is an 

 imposture, and is curable by treatment at the hands of the 

 magistrate. 



These, then, are the fundamentals of medicine that are here 

 examined and defined : 



1. Function. — The duty, office, work, or part that is per- 



formed by an organ or tissue. 



2. Extrinsic Function. — The work done by an organ or 



tissue for the other parts of the body, or for the body 

 as a whole : the part the organ or tissue plays in the 

 bodily economy. 



3. Intrinsic Function. — The maintenance and repair by an 



organ or tissue of its own structural integrity. 



4. Disease. — Disorder of function. The wrong or defec- 



tive execution of function, either extrinsic or intrinsic. 

 Also the signs and results of such defect or disorder. 



5. Symptom. — A perceptible sign or manifestation of 



disorder or defect of function. 



6. A Disease. — A mental construct or concept, consisting 



of a symptom or group of symptoms, correlated with or 

 by a single intra-corporeal cause, known or postulated. 



7. A Sub-Disease or Symptomatic Disease. — A symptom 



or group of symptoms correlated with or by a struc- 

 tural change which is part of an existing disease. 



