1913.] arising from Rivalry of Antagonistic Reflexes. 237 



machine, kept in a state of constant excitement, the electricity is given off 

 periodically. The dry air between the machine and the conductor held near 

 it impedes progress of the electricity to the conducting body until the 

 electricity accumulates in quantity to overcome the impediment offered in its 

 course, and the electricity escapes in a succession of sparks. This is an 

 illustration of how the current of the nervous principle may be rendered 

 periodic?'* A well-known application of this explanation to a particular 

 case of nervous rhythm was that given by Rosenthal! for the inhibitory action 

 of the superior laryngeal on the respiratory centre (1862). He concluded that 

 the stream of nervous impulses from the constantly discharging and blood- 

 stimulated respiratory centre meets a resistance to its outflow and thereby 

 becomes rhythmic, much as does a stream of air passing out from a tube under 

 water {op. ext., p. 242). He described the function of the superior laryngeal 

 nerve as being to increase this resistance and thus slow and deepen the 

 respiratory movements ; and the function of the rest of the vagus as being to- 

 lessen the resistance and thus render the respiratory rhythm less deep and 

 more frequent. He argued that other inhibitory nerves act on their respective 

 mechanisms in the same manner as does the superior laryngeal On the: 

 respiratory centre. 



When a skeletal muscle's reflex contraction is partly antagonised by a 

 reflex inhibition insufficient to suppress it entirely, the contraction thus 

 moderated by inhibition often shows oscillations. A. Forbes* has put the 

 question whether these oscillations may not mean that nerve-impulses 

 constantly generated by the reflex excitatory nerve break through the> 

 inhibitory resistance periodically, just as, on Rosenthal's view, do the inspiratory 

 impulses from the respiratory centre. 



Undulations tend commonly to appear in reflex contractions obtained under 

 concurrent reflex excitation and inhibition,^ and both T. Graham Brownjl 

 and ForbesH have independently called attention to features in them. Of 

 such undulations two main forms may be distinguished, and it seems at 

 present well to regard the two separately, although the same principle of 

 production may underlie both. 



In one form, the undulations are smaller, more rapid, less regular, and 



* John Miiller, 'Handb. d. Physiol.,' 1835, vol. 11, p. 77. 



+ 'Die Athembewegungen u. ihre Beziehungen zum Nervus Vagus,' Berlin, 1862. 

 % 'Eoy. Soc. Proc.,' July, 1912, B, vol. 85, p. 289. 



§ 'Eoy. Soc. Proc.,' 1909, B, vol. 81, p. 268 ; cf. also 'Quart. Journ. Exper. Physiol.,' 

 1908, vol. 1, p. 7. 



|| 'Koy. Soc. Proc.,' 1912, B, vol. 85, p. 278. 

 1 Ibid. 



s 2 



