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functions, yet a better definition cannot be given without an 

 elaborate description of that state of all the organs respectively, 

 which may be agreed to constitute a healthy condition. Thus, 

 beginning with the head, it may be said the condition of health 

 requires that the head should have no tumours on it, that the skull 

 be covered by the scalp, that the scalp be supplied with blood, 

 that its structure should be of such a kind that its sensibility and 

 its life should be so and so; and then an average thickness proper 

 for the cranium must be defined; and then of the contents of the 

 cranium, &c. ; all of them endless themes. Let us therefore be 

 content with a looser, with the loosest, definition, rather than 

 incur so tedious a history. Let us say that health is one condition 

 of the body and disease another; and that men are so well agreed 

 about the use of these terms, that they do not require to be any 

 further explained. But, if it should be resolutely insisted that 

 some standard between health and disease should be established, 

 we shall, in the respective instances, readily discover such a 

 criterion, although an universal one cannot be proposed, It has 

 indeed been said, to this effect, that health is such a condition of 

 an animal as is agreeable with all his purposes. It then comes to 

 be asked what are his purposes, as, for example, those of a man 1 is 

 the art of flying one of his purposes'? no: why? because he is 

 not provided with the organs ; in the same manner, walking or 

 running would cease to be among the number of his purposes, if 

 he should happen to have lost his legs. 



4. According then to this common understanding or consent, 

 to which we have referred the definition of health and disease, 

 health is a certain state (settled by this common agreement or 

 understanding), and disease is a. change or modification of the state 

 of health. 



5. Health is the effect of the causes which have to some 

 extent been traced in the preceding sections. These causes con- 

 cur to identify the condition of health. Disease is a modified or 

 altered state of the causes which produce health. 



6. An healthy condition of an animal is the sum of the causes 

 which concur to this end : so, if one only of these causes should be 

 90 modified as to impair this concurrence, the animal may then be 

 said to be unhealthy or diseased. Yet, under a modification so 

 trifling as this, many parts, or many, perhaps by far the largest 

 proportion, of the causes of the animal may not participate in this 

 modification, or may be in a state of health. This distinction 

 indicates the first step of analysis. If the healthy identity of an 

 animal is dependent upon all his parts, a deviation from this con- 

 dition in any will make an unhealthy state of the animal. As 

 then we have analysed his parts,, with a view to come at the 

 minuter knowledge of the conditions of health, so we must descend 

 also to the state of constituents, in tracing the history of disease. 



7. Disease is primary, secondary, or general, aud it is acci- 

 dental or spontaneous: primary, as when it originates in. ojie seat 



