APPARENT ANTITOXIC ACTION OF SALTS 121 



effect upon skeletal muscle of various mixtures in which the chlo- 

 rides of lithium and magnesium were the principal ingredients.* 



When a muscle is exposed to a bath, there are at least three ways 

 in which we may estimate the effects of the immersion. First, 

 we may simply find out the duration of its irritability, noting when 

 in the course of hours or days it ceases to respond to strong stimuli ; 

 in this case we should apply shocks only occasionally, and the muscle 

 would not have performed much work. Second, we may exhaust 

 the muscle by severe and repeated stimulation after a longer or 

 shorter period in the bath, and thus obtain a rough measure of its 

 working capacity. For this purpose a work-adder may be used, 

 or the area of the record traced on a slowly moving surface may 

 be noted. Third, we may determine the irritability of the immersed 

 muscle from time to time by varying the strength of the stimuli 

 and recording the position of the secondary coil corresponding 

 to maximal and minimal responses. We kept all three points in 

 view, but placed emphasis upon the second the total performance 

 of the muscles when stimulated strongly and frequently. Some- 

 times a thousand contractions went to form a record. 



All our experiments were comparative. We used companion 

 muscles from the right and left legs of frogs, so that we might have 

 controls which at the outset should be practically identical with 

 their fellows in potential energy and irritability. The muscles 

 worked upon equal levers similarly adjusted and weighted. The 

 stimulating current passed through both preparations, traversing 

 each lengthwise and being led from one to the other by a flexible 

 bit of metallic tinsel. In most of the experiments the shocks were 

 derived from a cog-wheel interrupter driven by clock-work. Break- 

 shocks alone were brought to bear on the tissue, the makes being 

 eliminated by a mechanical device. The stimuli were applied 

 from 30 to 60 times per minute. Usually the stimulation was supra- 

 maximal, and the muscles were out of the solutions when working, 

 so that there could be no scattering of the current. They were 

 frequently washed during their prolonged series of contraction 

 The solutions were made from salts of high purity and tested as 



*Sometimes the chlorides of calcium and potassium were also present in the small percentages of a 

 Ringer's mixture. Their presence did not affect the general nature of the results, and it is needless to 

 dwell upon the minor modifications which they probably brought about. 



