34 On the Effects of Certain Physical and 



dorsal muscles were observed, on breaking it none. On con- 

 necting the wires of the completed circle, still greater move- 

 ments of the dorsal muscles occurred, together with reflex 

 movements of all four extremities. 



Ex, 13. We prepared the frog in the same manner as be- 

 fore, and passed the current from the small battery in the 

 contra-incident direction, through the dorsal incident nerves. 

 After the lapse of five minutes, considerable muscular con- 

 traction was observed on breaking the circuit, and slighter 

 on remaking it. When the circuit was broken, no effect 

 was observable on connecting the wires ; but on remaking 

 the circuit and connecting the wires, there were energetic 

 muscular movements of the body, and reflex movements of 

 the lower extremities. 



It may be a question whether there be, in the experiments 

 already detailed, any evidence of an electrogenic state of the 

 incident nerves. The difference of degree in the effect ob- 

 served on completing the Voltaic circuit, and on connecting 

 the wires whilst this circuit is perfect, can, however, scarcely 

 be attributed to any other cause. It may not be in the nature 

 of an incident influence to induce forcible tetanoid spasms. 

 In the frog the incident nervous tissues are also on too small 

 a scale for this purpose. Ordinary reflex actions were readily 

 induced by irritating the integuments raised from the back, but 

 still attached through the incident nerves ; but nothing like 

 the continued muscular action seen in the decapitated turtle, 

 on pinching the extreme parts of the fin or extremities. 



Ex. 14. The frog was prepared as before, and the current 

 was passed along the incident nerves, in the contra or inci- 

 dent direction. There was, in the very first instance, consi- 

 derable movement and reflex action on completing the circuit ; 

 still more, the current being complete, on connecting the 

 wires of the Voltaic apparatus. These phenomena ceased 

 in a very shoit space of time. 



I was still anxious to obtain more unequivocal results in 

 my attempts to induce the electrogenic state in incident nerves, 

 those nerves which my former labours had first detected, and 

 recommended to the attention of physiologists. 



