DEFINITION OF DISEASE. 3 



quantity of food that would keep another thin and poor. " In 

 plain words, health does not signify any fixed and immutahle 

 conditions of the body, nor does health necessarily imply the 

 integrity of all the bodily organs : it is not incompatible with 

 great and permanent alterations, nor even with the loss of parts, 

 that are not vital. Our comprehension of health being thus 

 indefinite, our idea of disease must be indefinite also ; and the 

 best definition that can be given of it is, that it is a deviation 

 from the state of health, consisting generally in a change in the 

 properties or structure of any tissue or organ, which renders 

 such tissue or organ inadequate to the performance of its healthy 

 actions and functions." — (Watson.) 



It must not, however, be supposed that disease, as exhibited 

 by an unnatural or morbid condition, and by phenomena which 

 are seemingly abnormal, is unnatural in itself; for in reality 

 disease may be looked upon as the natural expression of a com- 

 bination of conditions, the essential and proper consequences 

 of some cause or influence which has acted, or is acting, upon 

 the animal body. To adduce a familiar example, let us suppose 

 a blister is applied to the skin : the inflammation of the skin 

 which is thus produced is certainly unnatural, and may with 

 propriety be called disease ; but if we look further into the matter, 

 we can easily understand that the inflammation, vesication, or 

 even ulceration so induced are the natural results of the action 

 of the irritant, — in fact, the proper and healthy reaction of a 

 healthy organism to the irritation of the blister. The absence 

 of this reaction — the skin remaining healthy — under such con- 

 ditions would indeed be unnatural, unlocked for, and incomiDre- 

 hensible. This may be taken as a type of cause and effect in all 

 diseases : it is not the inflamed condition of the skin, nor even 

 the constitutional disturbance which may be caused by a severe 

 blister, but the presence of the blister that is really unnatural. 

 This illustration, homely as it may seem, is important, as all 

 real adv^ancement in prevention and treatment is based upon 

 a due appreciation of the causes of disease ; for in the past, 

 more particularly in Veterinary Medicine, the aim and purpose 

 of practice has been directed to the treatment of symptoms — to 

 deal with effect, often ignoring the cause. Hence the many 

 systems, founded on erroneous bases, by which diseases have 

 been combated, have been productive of much harm. 



