165 



continue their functions unimpaired, though the inferior portions 

 may be removed. Such, I say, may be the result of a relation be- 

 tween the injury and the properties of the inferior portion without 

 giving occasion to infer from such facts that the inferior is con- 

 tinually deriving properties from the superior parts of nerves. 

 But if the inference is questionable in this example, what shall we 

 say of it in others? Without pushing this point any further at 

 present, let us see the amount of that which is absolutely proved 

 by these facts, which is simply this: 



12. That there subsists a relation between the properties of 

 different seats; that, by an influence upon, or destruction of, those 

 in one seat, those of another will either be modified or made to 

 cease. If we would have unquestionable proofs of a perpetual 

 communication among the vital properties (similar to that of the 

 blood, which is perpetually passing from one set of vessels into 

 another), we must derive them from some other source. 



13. Although I have objected to some inferences, as necessa- 

 rily true, which have been made from the effects of the division 

 of nerves, yet I would not be understood to deny their probability 

 in general instances. I have mentioned that which might be 

 urged as a refinement upon scepticism, merely to furnish an indi- 

 cation for an inquiry of the strictest possible kind. Meantime, in 

 addition to the evidence which is afforded by the consequences of 

 the division of nerves, we possess also that afforded by the general 

 fact, that no insulated portion of an animal structure can live. 

 Hence it may be presumed (but how fairly we shall presently 

 examine) that the life of no part is perfect of itself, or that it is a 

 specimen of independent life. If however this conclusion were 

 granted, it would follow further that the life existing in one sphere 

 is invariably dependent upon a supply of properties which it re- 

 ceives from some other, which, as will presently appear, is not 

 agreeable with truth, 



14. But, it will be asked of this additional proof, whether the 

 life that ceases in an insulated sphere may not be destroyed by an 

 agency conferred by the means which separated this portion from, 

 the rest? To this I reply that the supposition is not in agreement 

 wilh fact. If a muscle be cut transversely, half through the 

 divided fibres both above and below will live while there is com- 

 munication with living parts; but if the limb be amputated at the 

 same point, then the life of the same identical fibres, which have 

 sustained the very same operation, will become extinct, that is, a 

 portion of structure will live while connected with the rest, under 

 precisely that agency which would occasion its death when separa- 

 ted from its living connections. 



15. This last observation appears to give additional validity 

 to the inference before said to be liable to some sceptical doubts, 

 It is to be inquired what sort of criterion we possess, for dis- 

 tinguishing between changes produced by accession, and those 

 Arising from privation iu general instances. The subject is full of 



