340 PRACTICE OF PHYSIC. 



the same disease, by directly destroying the mobility of the ner- 

 vous power. Such causes seem to be the mephitic air, arising 

 from fermenting liquors, and from many other sources ; the 

 fumes rising from burning charcoal ; the fumes of mercury, of 

 lead, and of some other metallic substances ; opium, alcohol, 

 and many other narcotic poisons : to all which I would add the 

 power of cold, of concussion, of electricity, and of certain pas- 

 sions of the mind. 



MCXVI. None of these poisons or noxious powers seem to 

 kill by acting first upon the organs of respiration, or upon the 

 sanguiferous system ; and I believe their immediate and direct 

 action to be upon the nervous power, destroying its mobility, 

 because the same poisons show their power in destroying the 

 irritability of muscles and of the nerves connected with them, 

 when both these are entirely separated from the rest of the 

 body. 



MCXVII. It appears to me probable, that the apoplectic 

 state in some degree accompanying, and almost always succeed- 

 ing, an epileptic paroxysm, does not depend upon compression, 

 but upon a certain state of immobility of the nervous power, 

 produced by certain circumstances in the nervous system itself, 

 which sometimes seem to be communicated from one part of the 

 body to another, and at length to the brain. 



" I have mentioned, as a cause of compression, certain tumours 

 within the cranium, sometimes of different kinds. But in many 

 cases where such tumours have been attended with apoplexy and 

 palsy, they are not of such a size as to allow us to think that 

 they were the cause of any general compression of the brain. 

 If I remember right, Morgagni gives cases of apoplexy and 

 palsy, where seemingly the whole cause of compression was not 

 above two spoonfuls of blood effused. In such cases it is diffi- 

 cult to understand how any general compression of the brain can 

 be produced ; or how the origin of the nerves can be any way 

 affected. Now, I think that in such cases we must suspect that 

 a partial compression is sufficient to produce a pretty general 

 collapse over the whole medullary substance." 



MCXVIII. The same observation may be made with respect 

 to many instances of hysteric paroxysm ; and the circumstances 

 both of epileptic and hysteric paroxysms, ending in coma, or a 



