1906.] 



Special Excitable Substances in Cells. 



173 



results as regards the equal irritability of the different regions of the 

 muscle.* 



On Kiihne's view, then, curari readily paralysed a part of the nerve in the 

 muscle a short distance before its ending ; with an increasing dose of curari, 

 the paralysis spread both down and up the nerve-fibres till finally the whole 

 was paralysed ; the proper irritability and contractility of the muscle 

 remaining the same. 



Some years later, Pollitzer,"f working in Kiihne's laboratory, confirmed the 

 unequal irritability of different parts of the sartorius muscle, and found that 

 the irritability corresponded with the number of nerve endings described 

 by Mays in the different regions. He supported Kiihne's view that the 

 primary action of curari was not on the actual terminations of the nerves, 

 and suggested that it might be on the cement substance of the last node, and 

 not directly on either nerve ending or axis cylinder. 



The difficulties in understanding the action of curari brought out by the 

 work of Kiihne and Pollitzer have had but little influence either on opinion 

 or on the course of investigation, and I am uncertain whether Kuhne himself 

 adhered to his original view. Almost universally the simple and more 

 intelligible theory has been taken that the axis cylinder of a nerve-fibre, 

 in branching to make the nerve ending, alters its properties and is more 

 susceptible to the action of various poisons. 



A recognition of a difference in the properties of nerve endings and 

 nerve-fibres has coloured the interpretation of physiological facts more and 

 more as further facts have become known. Thus when the phenomena of 

 fatigue were investigated, the nerve endings came to be considered as more 

 liable to fatigue than the muscle, and as being different from nerve-fibres 

 in which fatigue was produced with difficulty or not at all. The theory has 

 also been applied to the connection of nerve-fibres with unstriated muscle, 

 with gland ceils, and more recently to the connection of nerve cells with 

 one another. In all these cases, though to a varying degree, the nerve 

 endings are commonly held to be especially affected by numerous poisons 

 and as especially liable to fatigue. Lastly, in some cases the phenomena 

 observed during the degeneration of a nerve have been attributed to the 

 vitality of the nerve ending being greater than that of the axis cylinder 

 of the fibre in the nerve trunk. 



* Sachs ('Reichert and Du Bois Reymond's Archiv,' 1874, p. 51) stated that, after 

 curari in sufficiently large amount, the irritability of all parts of the muscle became the 

 same. Pollitzer {op. ext. infra) found that maximal doses of curari lowered the irritability 

 of all parts of the muscle, but that the curve of irritability of the several parts was like 

 that of the normal muscle. 



t Pollitzer, ' Journ. of Physiol.,' vol. 7, p. 274, 1886. 



