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necessary, are not so immediately essential but that life may for a 

 time be preserved without them. Thus, a severe injury of a leg 

 may produce death in twenty-four hours, and a wound of the sto- 

 mach or bowels may produce death in the same time: in the former 

 case, death is produced by injury of a part which has no function 

 upon which the life of the system depends; in the latter case, the 

 injury takes place in an organ which has a function necessary to life ; 

 but the exercise of this function, viz. digestion, may be suspended 

 several days without occasioning death. The consecutive processes 

 which follow these injuries are merely additional instances of secon- 

 dary disease, terminating in death. 



4. The only question or difficulty which I feel disposed to 

 suggest, with respect to mechanical injuries, is concerning the mode 

 in which they produce the phenomena assignable only to spiritual 

 change. We find that the point of a needle applied to the skin 

 with a slight pressure, so as not to penetrate the skin, produces pain : 

 we find that a bullet going through the brain will immediately 

 destroy its function, as a consequence of which universal death 

 succeeds. And we observe with respect to these phenomena that 

 any mechanical agent, which produces the same mechanical effect 

 upon the structure, will produce the same effect upon the properties 

 of life. Hence, the relation is not with any peculiar properties 

 belonging to the instrument which inflicts the injury, but with the 

 effect of the injury, or with the condition of the textures, &c. 

 which the injury has produced, and the capability to produce 

 which may be common to many agents, very different in their gene- 

 ral character. To reduce the question, we will ask why the life of 

 a part suffers any change not imputable to loss of blood, from a 

 mere solution of continuity in the structures, as by the thrust of a 

 small-suord? 



5. The palpable effect of such injury is to separate parts which 

 were before united, in consequence of which inflammation, with its 

 accompaniments, pain, increased heat, &c. supervene. The first 

 effect is a mechanical separation of a structure before united ; the 

 subsequent phenomena are those which can be produced only by 

 spiritual change. It is obvious that the spirit, or the imperceptible 

 properties allied with the structures, would suffer no change by the 

 passage of a small-sword through the sphere in which they exist, any 

 more than the air or the still grosser fluid, water; unless indeed the 

 agent possessed properties related with the spirit, which may affect 

 it independently of the mechanical injury, which, for the reason 

 above assigned, is not the case. The only conditions of the main- 

 tenance of the identity of the living principle are, the existence of 

 this principle, and the presence of blood. Now the principle lives in 

 the separated surfaces, and in them may be supplied with blood. If 

 then the principle suffers that change which constitutes one of 

 disease, it suffers this change from one of three effects of the in- 

 fliction of the injury. 



