ADVANCED EXPERIMENTAL PHYSIOLOGY 



315 



nerve (b). On the other hand the effect of electrical stimulation of the 

 nerve (a) upon the nerve (b) is not due to simple escape of electrical 

 current, for if a moist thread be tied at (a') no contraction of the 

 muscles supplied by the peroneal nerve will be obtained when the nerve 

 is stimulated at (a). A. moist thread will not block the passage of an 

 electrical current, but it destroys the physiological continuity of the 

 nerves and thus prevents the extension of the electrotonic current. 



FIG. 193. Diagram of the experiment Known as "paradoxical contraction." 



In certain cases, when the tissues are very excitable, the so-called 

 " paradoxical contraction " appears to be due to the excitation of the 

 nerve-fibres (b) by the action-currents of the adjacent nerve-fibres at (c). 

 The current of action of one nerve stimulates another nerve. 



CHAPTER XL 



THE RELATION BETWEEN MUSCLE AND NERVE. THE 

 INDEPENDENT EXCITABILITY OF MUSCLE. 



IN addition to the experiments which have been described in the 

 elementary course (page 48), the following experi- 

 ment upon the sartorius muscle should be performed. 

 The sartorius muscle lies on the ventral surface of 

 the thigh (Fig. 21), and its outlines can be made 

 distinct by sponging it with the frog's heart full of 

 blood. The muscle is carefully dissected out and 

 will contract when its nerve, which passes into the 

 muscle at the middle of its inner border, is cut across 

 by the scissors. If the muscle be placed between two 

 glass-slides and examined under a microscope, the 

 distribution of its nerve can be seen to resemble 

 that shown in the diagram (Fig. 194). The finer 

 branches of the nerves and even the end-plates can 

 be more readily seen if the muscle be treated with 

 acetic acid. There are no nerves in the terminal 



FIG. 194. ^- Dia- 



f its 



