1909.] 



Alcohol, Ether, and Chloroform, etc. 



549 



surrounding the muscle, which is traversed by only a small fraction of current. 

 The effect of varying the length of column is easily shown by adding or 

 taking away fluid while a series of contractions is in progress. I have, there- 

 fore, always been careful to replace fluids by pipette as exactly as possible. If, 

 as has sometimes happened, the difference of excitability and contraction in 

 two muscles has been grossly unequal— even more so than in the case of the 

 pair of muscles used for the record of fig. 1 — I have thought it permissible to 

 adjust the tubes in their holders upwards or downwards so as to alter the 

 current lines in suitable degree. But once fixed in position, the tubes must 

 not be shifted again ; the level of fluid must be kept unaltered throughout 

 experiment. 



Differences of resistance between different fluids are in most cases of little 

 moment, e.g. a cubic centimetre of chloroform does not increase the resistance 

 of a litre of saline enough to influence the exciting current traversing the 

 muscle. In some cases, however, differences of resistance may be such as to 

 affect the current distribution and the response of the muscle, e.g. a 10-per- 

 cent, solution of alcohol in saline has an appreciably higher resistance than 

 saline alone. 



It may be objected to the method that excitation is not restricted to the 

 muscular substance, but includes intramuscular nerve tissues. To meet this 

 objection I compared the effects on fully curarised and on uncurarised muscle, 

 and found that they were indistinguishable. This fact, however, is of little 

 weight, inasmuch as immersion in normal saline is of itself sufficient to 

 remove the effect of curarisation. But, on reflection, the objection itself is 

 of little weight. As is well known, the direct excitability of muscle outlasts 

 its indirect excitability vid nerve; loss of all contractility is of necessity 

 loss of direct excitability, and whatever might be said as to the beginning of 

 an observation, there can be no doubt that at its end we are dealing with 

 muscle and muscle only ; even at the beginning of an observation, since we 

 are using a strength of current more than sufficient to excite muscle as well 

 as nerve, the contraction must be by direct muscular excitation ; and even if 

 it were not, if it were by indirect excitation at the beginning, the com- 

 parative results of, e.g. the action of ether and chloroform, would remain 

 acquired. To use as a test object excitation of the nerve of a nerve muscle 

 preparation would, of course, be a different method, by which the tissue 

 specially under investigation would be the end-plate. To use as an index the 

 minimal strength of stimulation giving contraction would again be a different 

 method, by which at first indirect and later direct excitability would be 

 investigated. I have avoided both these proceedings, and have preferred to 

 follow the method described because it is more practicable and less ambiguous 



VOL. LXXXI. — B. 2 B, 



