OF VITAL MOTION. 99 



easy to believe that the air passages remain contracted 

 in consequence of the absence of a vital stimulus 

 the natural operation of which is to produce dilata- 

 tion, than that they are stimulated to this state by 

 any positive action of the gas. It is difficult, indeed, 

 to suppose that the gas has produced contraction in 

 passages into which it has not entered. 



In relation to the effects of other chemical agents 

 we know but little. We know, however, that in order 

 to the proper mobility of muscle, the peculiar state 

 and constitution of the fibre, in relation to moisture, 

 must be preserved, and that in absence of this the 

 mobility will be nullified. When a fibre is macerated 

 in water it is found to become pulpy, changed in colour, 

 and otherwise altered. It is no longer with a normal 

 fibre that we have to do, and we must not reason as 

 if it was so; and if, therefore, under these cir- 

 cumstances, the mobility be lost, we may argue that 

 this result is the natural consequence of the altered 

 constitution of the fibre. Alcoholic, alkaline, or acid 

 solutions are also found to alter the quality of the 

 fibre in a peculiar way. In speaking, therefore, of 

 the effects of a solution of opium or any other drug, 

 the effects of the menstruum are not to be forgotten ; 

 and as this has been the case in too many instances, 

 it is necessary that more careful experiments be insti- 

 tuted before we can be satisfied that we possess a 

 proper knowledge of the true action of these drugs. 



H 2 



