Disease may thus properly be defined, any change of the healthy state and healthy function of parts. If any one urge, that disease implies the action, not the state of parts, I grant it; but must observe that _change_ of state is action, and change of healthy state is evidently morbid action or disease, whether it arises from within or without, whether suddenly from external and accidental causes, or more slowly within the body and in dependence upon other previous derangement. Indeed to trace any disease back through previous derangement is actually to trace out other diseases, and to define any disease from others thus traced out, is to abandon those distinctions which separate the termination of one disease from the commencement of another. If any one still assert, that disease is not change of the state but change of the action of parts, and urge that those accidents which depend on external causes, as fracture, considered in themselves, are not disease, I should say, were this even proved, it could only affect my arrangement by giving the term injuries, instead of diseases, to the first class. As, however, it seems to me that they may justly be named diseases, and that practically considered they are precisely the same, I shall retain that term. Thus, we shall have a fairer view of the interesting analogies which, as will be seen, exist between the animal, vegetable and mineral worlds. Now, if disease consist in change of function, different diseases must either consist in different changes of the _same_ function or in the changes of _different_ functions; the former, viz. different changes of the _same_ function, as being a more minute division, making evidently the genera which are subordinate; the latter, viz. changes of different functions, as being more general, forming the orders which include these genera. From the inspection of the table, and a consideration of the nature of disease, it will appear, that whatever is commonly reckoned one disease, is generally, perhaps always, three; thus fracture is always accompanied by inflammation and pain; and while the simple fracture is a disease of diminished support, the inflammation caused by it is a disease of increased circulation, and the pain caused by it a disease of increased impression.