MUSCLES, NERVES, AND ELECTRICAL ORGANS. 185 



towards the abscissa, so that it first approaches the lower curve 

 and then separates from it, as shown in Fig-. 7. It is impossible 

 here to follow further these particulars which are still very im- 

 perfectly investigated. The most important result from them con- 

 sists in the necessity of assuming the coexistence of both polarisa- 

 tions in muscle, from which it follows that the apparent magnitude 

 of the resulting positive or negative polarisation teaches us nothing 1 

 of the true magnitude of each of the component polarisations, for 

 the result we obtain represents the difference between the two 

 components, either of which components may be greater than the 

 difference itself. 



10. On the Influence of the Direction of the Primary Current 



on the Secondary Electromotive Action of Muscles. 

 I pass over the casual observations and the long list of preparatory 

 experiments which led me at last to the view that in a regular 

 muscle, for instance our group of muscles, the upper half exhibits 

 stronger positive polarisation in an ascending, and the under in a 

 descending direction. The best means of proving this consists in 

 sending the primary current alternately in both directions, first 

 through one half of the muscle and then through the other, allowing 

 exactly the same period of time to elapse between each momentary 

 current, in which case polarisation disappears with the exception 

 of a small residue which is then compensated. If its complete 

 disappearance is waited for, so long a pause becomes unavoidable 

 after each experiment, that great inconveniences arise. If you 

 wait on each occasion, without reference to time, till the polarisa- 

 tion reaches a certain or absolute value, that is to say till it 

 either sinks to a fraction of its original value or to a certain 

 number of divisions of the galvanometer scale, or ' degrees of the 

 compensator/ all kinds of uncertainties are met with. With a short 

 time of closure, and a strong current, the first method of experiment 

 always gives the best result. In any case it is to be preferred to 

 the statistical method which consists in obtaining a mean value 

 for the positive and negative polarisation in both halves, by experi- 

 ments on constantly renewed muscles, so that the current is only 

 once passed in one direction through each half of the muscle. The 

 variations in the strength of the primary current due to irregu- 

 larities in conduction are, as we have already seen (Sect. 7)> so 

 considerable in spite of every care, that for their compensation an 

 enormous number of experiments would be necessary. 



