168 



Dr. N. H. Alcock. 



[Apr. 9, 



the limiting membrane — has a directive or semi-permeable action, letting 

 through some ions more freely than others, the general behaviour of the 

 apparatus would approximate to the scheme. If, then, chloroform destroys 

 the semi-permeable mechanism (perhaps in the manner suggested by Meyer* 

 and Overtonf) every sort of ion could wander freely in any direction, and so 

 the whole tissue would become isoelectric. Further, this destruction would 

 be equivalent to a diminution of viscosity, and so would account for the 

 great increase in conductivity observed in Series III. 



' This must be regarded merely as a sketch of what is possible rather than a 

 finished hypothesis ; still this view presents certain problems in a manner 

 that will admit of a solution which will either prove or disprove the suggestions 

 here advanced. 



At any rate, the experiments show : — 



(1) That there are certain structures acting as semi-permeable membranes. 



(2) That chloroform inhibits or destroys their functions. 



Relations with Part I and Alternative Theories. 

 It will be remembered that in the consideration of the action of chloroform 

 (and anaesthetics generally) on isolated nerve some phenomena were found 

 which bear a relation to those now under consideration. Summarised they 

 are as follows : — 



(1) CHC1 3 acting on a nerve produces the same electrical effect as an 

 injury. 



(2) CHCI3 produces less than 2 per cent, alteration in resistance. 



If the hypothesis be adopted that there are in the axis cylinder of a nerve 



certain ions already present, it is plain that the action of the anaesthetic 



is the same on nerve as on skin, namely, that a semi-permeable apparatus 



is rendered completely permeable. It is not perhaps clear from the 



experiments on nerve alone whether this hypothesis is to be adopted 



or the alternative, that fresh ions are split off from the proteid by the 



action of the anaesthetic, but as it has been shown above that in the case 



of skin it is necessary to suppose the existence of a semi-permeable 



membrane, there is reason to suppose that this is the case in nerve also, 



and in fact it is not possible to create such a potential difference as is found 



in the case of nerve without some such arrangement, whether fresh ions are 



formed or no4 



* Meyer, ' Schmiedeberg's Archiv,' 1899 and 1901. 



t Overton, ' Studien iiber die Narkose,' Jena, 1901, etc. 



X On the conditions under which ions can exist in the axis-cylinders of nerve-fibres, see 

 Macdonald, 'Boy. Soc. Proc.,' vol. 76, B, p. 322, and Macallum and Menten, loc. cit, 

 vol. 77, B, p. 165. 



