80 



PRACTICAL PHYSIOLOGY 



iliac end is divided into two portions (Fig. 75). Stimulation with a 

 weak induction shock at (a) or (a'), when there are no nerve-fibres, will 

 produce a contraction of the one half of the muscle. Excitation, how- 

 ever, at (b) or (V), where there are nerves, will evoke a contraction of 

 both halves. 



Gracilis Experiment. The gracilis muscle of the frog is in two por- 

 tions completely separated by a tendinous intersection (Figs. 21, 76). 

 Both halves of the muscle are supplied by a single nerve, the individual 



FIG. 75. Diagram of the sartorius 

 experiment to show the transmission of 

 a nervous impulse in both directions. 



Fio. 76. Diagram of the gracilis 

 experiment to show the transmission of 

 a nervous impulse in both directions. 



fibres of which divide and supply both halves of the muscle. Stimula- 

 tion of any kind at (a) or (a') where there are no nerve fibres causes 

 only the corresponding half of the muscle to contract ; but excitation at 

 (b) or (b') t where the nerves lie, will cause both halves to contract. 



CHAPTER XX. (Advanced). 



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 experiment upon the 

 eartorius muscle should be performed. 



The sartorius muscle lies on the ventral surface of the thigh (Fig. 21), 



