548 Dr. A. D. Waller. Comparative Power of [June 24 r 



Comparisons were systematically made (1) between alcohol and chloro- 

 form ; (2) between alcohol and ether ; and (3) between ether and chloroform: 

 Such comparisons were, whenever possible, made upon the same muscle, 

 preliminary experiments having shown that two or more successive intoxica- 

 tions, if not too profound, by the same strength of solution, are of equal 

 gravity. 



The principal indication of the comparative effects of reagents consists in 

 the rate at which the contractility is abolished in solutions (in 06 per cent. 

 ISTaCl in tap water) of various strengths. The rate and amount of return of 

 contractility in - 6 per cent. jSTaCl affords confirmatory evidence, of which, 

 however, we have not made systematic use, having done no more than note 

 the facts: (1) that at equal times of immersion the time required for 

 recovery augments with augmented strength of solution, and (2) that at equal 

 strengths of solution the time required for recovery augments with 

 augmented time of immersion. 



Comparisons may be established between : the effects of two solutions upon 

 the same muscle successively ; or between the effects of two solutions upon 

 two muscles simultaneously; and each kind of comparison has its own 

 obvious advantage and disadvantage. By the method we have adopted of 

 simultaneously recording the contractions of two muscles in series, we secure 

 the advantage of both plans, and minimise the disadvantage of successive 

 comparison by reversing the solutions on the two muscles. Other obvious 

 advantages of the double method are that we get double the number of 

 observations, and that we can readily tell whether an accidental irregularity 

 is due to the stimulus or to the muscle or to the solution. 



We may also compare the effects of different solutions upon different 

 muscles, but in such comparisons from muscle to muscle we must take care 

 that the conditions of observation are, as far as possible, identical. We may 

 not, e.g., compare fresh with stale muscle, nor muscles of greatly unequal bulk,, 

 nor muscles taken from healthy and unhealthy frogs, nor results obtained at 

 different temperatures. Nevertheless, comparisons of this order are practi- 

 cally available, for under similar conditions the results of experiment with a 

 given solution are closely similar upon different muscles ; the " idiosyncrasies " 

 of different muscles are not a very disturbing factor, although, as might be 

 expected, effects are more rapidly produced with very small than with very 

 large muscles. 



The two chief fallacies in their order of importance are : (1) a variation in 

 length of the column of fluid, and (2) a considerable variation of temperature. 



As regards the column of fluid, it is evident that this must be kept of 

 constant length during an observation, since the fluid forms a derivation circuit 



