130 PHYSIOLOGY. 



fused over the whole of nature, a quantity of electric matter, 

 which, however, in the ordinary state of most bodies, shows no dis- 

 position to a particular mobility in passing from one body to 

 another, so that though it is present, it does not show any dis- 

 position to motion ; but we can, by certain artifices, accumu- 

 late this electric matter in more considerable quantity upon the 

 surface of certain bodies, in consequence of which it can be put 

 in motion from one body to another, exhibiting the various phe- 

 nomena of electricity; and it is agreed upon among philo- 

 sophers to call this excitement, and to say that electricity is ex- 

 cited, and that such bodies are excited electrics; and all bodies 

 may be so either by being excited themselves, or by having 

 such bodies applied to them as are. So, in our medullary 

 fibre, there is a fluid which was present in the germ, but was 

 not excited; and it is in the excited state of this that I suppose 

 life to consist, and when it is no longer excited in any degree, 

 we call it the state of death ; and I can suppose, as in electricity, 

 that it may exist in different degrees. Thus, sometimes I can take 

 a stroke at a yard's distance from the surface of the body that is 

 excited, and show that the electric fluid extends to such a distance; 

 at other times we must come within a quarter of a yard, and 

 at other times we must come still nearer; and so it can pass 

 through various degrees till it is collapsed altogether. We can 

 say that there is more excitement in one case than in another, 

 and that the collapse may proceed to different degrees. So far 

 with regard to the analogy that explains the terms. But there 

 is another body in nature of a peculiar kind, viz. iron, which 

 may probably have a quantity of magnetic power constantly 

 present upon its surface. It does not show it to other iron, but 

 we can give it its attractive and repelling powers ; we can give 

 it its polarity, &c. Whether there are other bodies that are 

 capable of this peculiar excitement I shall not say, but it is 

 probable that the medullary fibre may be of that kind. I give 

 another illustration that will perhaps approach nearer. It is 

 now commonly enough supposed by philosophers, that the 

 phenomena of the attraction and cohesion of bodies depend up- 

 on a fluid surrounding them : if there is any thing in this at 

 all, it is capable of excitement in different degrees. Some bodies 

 are, for the purpose of attraction and cohesion, always excited, 



