66 



PRACTICAL PHYSIOLOGY 



2. Extra-Cardiac Nervous Mechanism. 



Carefully insert the electrodes connected with the other side of the 



. C. Vs. Hy. Br. 



FIG. 66. Diagram of nerves in the frog's neck. Dissection from behind. 



(Pembrey and Phillips.) 



G, Glosso-pharyngeal nerve ; C, Carotid artery ; Vs, Vago-sympathetic nerve ; Hy, Hypoglossal 

 [nerve ; Br, Erachial Plexus. 



commutator into the medulla, fixing them on the cork of the frog- 

 board by a pin. Tilt the bridge of the commutator to send the 



FIG. 67. Diagram of the origin of the vago -sympathetic nerve (V.S.). 



L.A.S. = levator anguli scapulae muscle. Ao. = aorta. 1, 2,3, 4=first to fourth spinal nerves 

 Sym.= sympathetic nerve. G.P. = Glosto-pharyngeal nerve. G. = vagus ganglion. (Gaskell. ' 



FIG. 68. Contraction of the frog's heart. The effect of weak stimulation of 

 the vago -sympathetic nerve. 



The. white line marks the duration of excitation. Note the latent time, the acceleration and 

 increased tone and the after-effect. The curve should be read from left to right. (Pembrey 

 and Phillips.) 



