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jcancc of such objects: the most that we can do is to reason upon 

 this change on rules of analogy, which, if these rules are universal, 

 as has been assumed on physical proof of those of causation, are en- 

 titled to the same reliance in this, as in other subjects of inference. 



3. Death happens either 



1st, From defect or modification of those causes which main- 

 lain life, and which have been sketched in our physiology; or, 



2nd, From the operation of certain related externals. 



4. Of the causes which maintain life, the first to be spoken 

 of are those which constitute the living spirit. All that we can 

 say of these causes is, that in one particular state they produce 

 the phenomena of life and health; that if this state is modified, 

 they produce the phenomena of disease; that a further, or other 

 modification of them is followed by death. We have seen, in the 

 article on Disease, that the origin of every spontaneous modifica- 

 tion of the living state js in the properties of life. The spirit is 

 constituted by many properties, among which subsist certain rela- 

 jtions: from the relations between these properties, changes take 

 place in their combinations, which are progressively continued, or 

 suspended, and renewed, by the operation of an external, or main- 

 tained by consecutive effects, as those of the material occasional 

 .causes, of disease; or maintained by spiritual assimilation, &c. 

 As the first modification of the healthy spirit might originate from 

 relations in its own properties, so .it is probable that the pro- 

 gression might be continued in this spiritual department, until the 

 identity of it is so far changed, as to be incapable of assimilating a 

 state of properties productive of the phenomena of life. But, in 

 general, death is preceded by changes in the material alliances of 

 life, which might contribute more or less essentially towards this 

 event. The case which comes nearest to exemplify the occurrence 

 of deatti, by the exclusive change of the spiritual state, is perhaps 

 furnished in some of the forms of mortification incident to old 

 people; where death suddenly happens in a part while it is still 

 supplied with the same arterial blood as other parts, and where 

 the textures are not perceptibly more impaired. 



5. Three conditions are required for the maintenance of life 

 in every seat: 1st, a healthy state of the principle of life; 2nd, 

 the integrity and fitness of the structures; 3rd, an adequate and 

 correct supply of well-formed arterial blood. As long as these 

 conditions are observed the state of life is maintained, and it con- 

 tinues until one or all of these conditions are infringed. 



G. Death commonly happens through the medium of disease: 

 when death takes place suddenly and spontaneously, without pre- 

 vious disease, the difference is, that whereas in disease the changes 

 preparatory to death are indicated by symptoms; in death, with- 

 put disease, the preparatory changes do not produce symptoms, or 

 they are latent; in which latter case, death follows predisposition. 



7. Disease and death agree in being modified states of life: 

 .but the state of disease is stjll productive of the phenomena o'f life; 



