The readiness with which a muscle responds to a stimulus depends both on the condition of the muscle itself, and on the terminations of motor nerves within it. A faradaic current readily stimulates the nerve-endings, but does not act at all readily on the muscle. The making and breaking of a constant current, on the other hand, has comparatively slight action on the nerves, but a powerful action on the muscle. One of the questions which arises most constantly in connection with the action of drugs is : - whether or not they paralyse the end of the motor nerves in muscle. This question was fully worked out by Bernard, and also independently by Kolliker, in relation to curare.

The same methods of experiment were adopted by both. They were twofold, and consisted :

1. In applying the poison to that part of the body alone which seemed affected by it, and seeing whether it produced its usual action.

2. In preventing it from reaching that part, and seeing whether its usual effect was then absent.

The first of these methods consisted in the local application of the drug to the muscles and motor nerves themselves (Figs. 52 and 53). The second consisted in ligaturing the artery of one leg in a frog, so as to prevent the poison from reaching the muscles and motor nerves in that leg (Fig. 54).

The advantage of the first method, viz. that of local application, is that it allows us to deal with only one organ at a time, and the results are therefore less complicated than those of the second method. In some respects it is better to begin with the second method and work back to the simpler from the more complex organs (p. 149).