PHYSIOLOGY. 73 



pieces. What the proofs are which this author adduces I cannot 

 say, as I never, by any means, could obtain a sight of his dis- 

 sertation ; I can only give the grounds of my conjectures. Bo- 

 relli, and other authors upon this subject, have computed the 

 force in living bodies ; and we have experiments upon the force 

 in dead animals by Hales and Muschenbroek ; and from these 

 compared, we find that the force in the living is vastly greater 

 than that in the dead fibre. But these experiments have not 

 yet been fairly established ; and so I give it as a matter of con- 

 jecture to be further prosecuted ; but, independently of this 

 calculation, there is some probability in the theory that I have 

 offered. It is the opinion of some of the greatest philosophers, 

 particularly the English, with Sir Isaac Newton at their head, 

 and of several of the foreign of the greatest rank, that the co- 

 hesion of bodies depends upon the presence of an elastic fluid, 

 which is more rare in the pores of bodies, and more dense up- 

 on their surface, by which the parts are kept together ; and 

 upon this doctrine, which there is no difficulty in admitting, 

 there is no difficulty in explaining the whole phenomena of in- 

 animate elastics ; and all that our theory requires, is to suppose 

 that this subtile elastic fluid is by various means excited to a 

 greater degree : we have some illustration of it in the case of 

 electricity and magnetism, which are only modifications of this 

 subtile fluid ; and we need only suppose that this elastic fluid 

 can be thus excited upon the nerves and muscular fibres of liv- 

 ing animals, and that, in consequence of a certain degree of 

 excitement, the nerves are rendered sentient ; and that by some 

 peculiarity of the muscular fibre, it can be accumulated in them 

 and occasion muscular action. Having thus stated the matter, 

 I acknowledge to you that there are difficulties with regard to 

 it, in establishing the fundamental facts and applying them to 

 the several phenomena ; but what we call the fluid of the nerves, 

 that upon which the living power, upon which both sense and 

 motion depend, is manifestly an elastic fluid of one kind or 

 other. 



" I go on to add another circumstance to obviate some of the 

 difficulties which might be offered. I say" 



If this is true, it will also explain why the force of cohesion in 

 muscular fibres is greater than that of the medullary fibres in any 



