144 ON NERVE-EXCITATION BY THE NERVE-CURRENT. 



used with success solutions of the haloid and neutral salts of the 

 alcalies and alcaline earths, alcohol, ether, anhydrous acetic acid, 

 saturated solutions of tartaric acid and of sugar gave only the 

 second kind of contractions. 



From all these facts it appears to me that Eckhard worked with 

 much less excitable preparations than I did. Although it was not 

 my intention to make a special study of the excitatory action of 

 fluids on the transverse sections of nerve, I incidentally made 

 experiments of this nature with various fluids. And I found not 

 only that concentrated solutions of sulphate of copper and sulphate 

 of zinc (which, according to Eckhard, produce no effect) do produce 

 effects in so far as they give contractions at the moment of their 

 contact with the transverse section, but also that the same effect is 

 obtained by the use of a concentrated solution of sodium chloride, 

 and of 06 / solution of the same, fluids which, according to 

 Eckhard, only give the second kind of contractions. Sulphuric 

 acid, of a strength of 10 / , gave me the same result. Like 

 Eckhard, I found the fixed alcalies especially active. 



A. small drop placed on a glass slip suffices for the production of 

 the contraction by contact with sodium chloride, caustic potash, 

 sodium carbonate, sulphuric acid, sulphate of zinc or of copper. I 

 have seen solutions of sodium chloride, or of caustic potash, produce 

 the effect when I had used for the purpose a tiny drop, sufficient 

 to moisten the transverse section only, or at most the very border 

 of the longitudinal surface in addition. I have not used such small 

 drops of other fluids. 



Now, although on account of what has been said above con- 

 cerning the effect of external closure of the nerve-current, I can- 

 not doubt that it plays an important part in the contractions 

 occurring at the moment of contact, I am not in a position to be 

 able to exclude the possible conjoint action of chemical stimulation. 

 It surprised me that fluids differing but slightly in conductivity 

 appeared nevertheless to behave quite differently as to the certainty 

 with which they provoke contraction by their application to the 

 transverse section. The great activity of the fixed alcalies may 

 perhaps be explained by this, that the nerve is more rapidly and 

 easily moistened by them than by other fluids, so that a more 

 rapid electrical change is produced in the nerve. But I must leave 

 it unsettled whether this is the reason of their apparently greater 

 efficacy. 



There are two circumstances which notably increase the difficulty 



