172 Prof. J. N. Langley. On Nerve Endings and on [May 24, 



to their endings in the muscles, he did not find that curari in large amount had any effect 

 on them, and he was unable to reconcile this -with his previous results. In fact, the 

 question of the action of curari on nerves before they enter muscle is still one for 

 discussion. 



The view of the special character of the nerve endings has been further 

 strengthened by histological observations on the changes occurring in the 

 nerve endings under the influence of curari. Kiihne described the living 

 nerve endings in the muscle of lizards as having more distinct outlines after 

 deep curari poisoning, and still more after slight curari poisoning and pro- 

 longed electrical stimulation of the nerves.* Miuraf stated that prolonged 

 (18 days) curari poisoning in the frog caused a dwindling in the size of 

 hypolemmal fibres. Herzen and OdierJ find that curari causes the hypo- 

 lemmal fibres of the frog to become varicose, and that the axons of the nerve 

 outside the muscle became covered with fine granules, the change decreasing 

 towards the centre. 



A variant of the general view was early put forward by Kiihne. Kiihne§ 

 noticed that the irritability of the parallel-fibred sartorius muscle of the frog 

 was not the same throughout. It was least at the ends, where, as he also 

 found, no nerves or nerve endings were present. It was greatest near the 

 point of entrance of the nerve. This, of course, might only mean that the 

 nerve was more irritable than the muscle. But he found that curari, given 

 in amount sufficient to paralyse the motor nerve to the muscle, did not 

 abolish the difference in irritability between the middle and the ends of the 

 muscle. This he considered could not be due to a difference in the muscle 

 itself, since if he passed a constant current through the nerve supplying the 

 muscle, the positive pole being near the muscle, so that the end of the nerve 

 was thrown into an electrotonus, the irritability of the muscle became the 

 same throughout. Consequently, he concluded that the terminal portion of 

 the nerve, and possibly the whole nerve ending, was not paralysed by an 

 amount of curari considerably greater than that required to block the passage 

 of nervous impulses. 



After a very large dose of curari, Kiihne considered that the 

 whole nerve ending was paralysed,|| although he obtained inconstant 



* Kiihne, 'Verb. d. Naturhist.-Med. Vereins zu Heidelberg,' N.F., III, 1882. 



f Miura, ' Virchow's Archiv,' vol. 105, p. 129, 1886. 



| Herzen and Odier, ' Arch. Intern, d. Physiol.,' vol. 1, p. 364, 1904. 



§ Kiihne, ' Miiller's Archiv,' 1860, p. 477. 



|| According to Kiihne, a saturated solution of sugar stimulates nerve but not muscle. 

 The solution caused contraction only when applied to those parts of the sartorius muscle 

 of the frog which contain nerve-fibres. This action was abolished by sufficiently deep 

 poisoning with curari. 



