Dr Alison on the Principle of Vital AJinittj. 283 



blood which enters the vessels of any part where inflamma- 

 tion has been excited, has peculiar properties impressed on 

 it, and even changes on its composition effected, merely by 

 coming in contact with the portions of vessels where that 

 process is going on, and with the portions of blood previously 

 subjected to it ; — that the exudation from inflamed vessels 

 acquires peculiar properties from the contact with the living 

 surface on which it lies, first arranging itself as an organized 

 structure, and then selecting and appropriating, from the 

 neighbouring bloodvessels, those materials by which it is as- 

 similated to the texture witli which it is connected ; — again, 

 that, in tiie sound state, every portion of matter which is de- 

 posited from the bloodvessels, to form part of a muscle or of 

 a nerve, immediately acquires the peculiar vital properties 

 of the part which it nourishes ; and, in the case of muscles, 

 even, that the change produced in a portion of a fibre by the 

 application of a stimulus, is instantly communicated to the 

 whole length of that fibre, and to many adjoining fibres. It 

 appears to be nearly in the same manner that every porti<3n 

 of carbon and water which enters into tlifi composition of any 

 living vegetable cell, acquires the power of exerting tbe same 

 vital affinities as actuated the matter which it replaces, or to 

 which it is added. 



IV. Another principle, at least equally important and cha- 

 racteristic, may be stated in regard to this communication of 

 vital properties to the materials which are added to living 

 bodies, viz., That such powers are imparted only for a brief 

 period of time, and that long before the time of the death of 

 the structure to which they belong, all those materials lose 

 the vital properties whicli have been given to them ; perhaps, 

 as has been lately stated, as a consequence of the exercise of 

 their peculiar vital powers, perhaps merely as a general law 

 of vitality ; but equally, whether the peculiar properties which 

 they acquire in living bodies are of the nature of nervous ac- 

 tions, vital contractions or attractions, or vital affinities. But 

 as this principle is best illustrated by reference to the pheno- 

 mena of excretions, we delay doing more than merely enun- 

 ciating it at present. 



