Nerve Endings and Special Excitable Substances in Cells. 171 



required to paralyse the motor nerve* did not paralyse either the sensory 

 nerves or the central nervous system, or the trunks of the nerves near the 

 central nervous system. He concluded that the primary poisoning effect of 

 curari was due to a local action on that part of the nerve which lies in the 

 muscle. 



He pointed out also a similar local action on other tissues in the case of 

 other poisons. Thus strychnine caused convulsions by an action on the 

 central nervous system, but did not appreciably affect the properties of 

 nerve-fibres or of muscles. And sulpho-cyanide of potassium destroyed the 

 irritability of muscles — so that on stimulating them electrically, or pinching 

 them or cutting them, no contraction could be obtained — but it had no 

 marked action on either the central nervous system or the nerve-fibres. 



Bernard's experiments thus distinguished a difference of behaviour in the 

 nerve trunks, in the branches of the nerves in the muscle, and in the muscle 

 itself, as well as (presumably) in the nerve cells of the central nervous 

 system. 



On the discovery of the nerve endings in vertebrate muscle, with their 

 characteristic appearance in each class of animals, the paralysing action of 

 curari on the peripheral branches of the motor nerves was naturally referred 

 to the endings, and thus the nerve endings were taken to be different from 

 the fibres from which they arose by division, and curari was said to paralyse 

 nerve endings. This view was strengthened by the prevailing opinion that 

 curari after prolonged action or in sufficiently large doses affected the nerve 

 trunks also, for if the nerve endings were specially differentiated parts 

 of the nerve-fibres it would be more reasonable to suppose that they would 

 be specially affected by curari if the nerve-fibres were affected to some 

 extent, however small, than if they were completely unaffected. 



According to Bernard, curari acted first on the " terminations " of the motor nerves, and 

 then, if in sufficient amount, gradually robbed the rest of the nerve of its irritability, 

 beginning at the periphery and spreading towards the centre. A paralysing action on 

 the nerve trunk was also found by Kolliker. Kuhnet observed that in frogs recovering 

 from slight curari paralysis the nerve first became effective near its end, and only later 

 near its origin from the spinal cord. Later,J however, in experiments on the nerves close 



results in his lectures. Whilst these lectures were in the press (' Lecons sur les Effets des 

 Substances Toxiques et Medicamenteuses,' Paris, 1857), and before Bernard's results were 

 generally known out of France, Kolliker published the observations he had made on the 

 action of curari (cf. ' Virchow's Archiv,' vol. 10, p. 3, 1856). His results agreed in general 

 with those of Bernard. 



* The phrase " paralysis of the nerve " is used in its customary sense to indicate that 

 on stimulation it does not have its usual effect. 



t Kuhne, 'Miiller's Archiv,' 1860, p. 477. 



X Kuhne, 'Ueber d. Wirkung des Pfeilgiftes auf die Nervenstamme,' Heidelberg, 1880. 



p 2 



