318 



Mr. J. S. Mucdonald. 



here only from the three experiments which seem to determine the 

 strength of the isotonic solution as showing a minor degree, an absence, 

 and a reversal of the condition. 



Experiment A. Sciatic Nerm of Cat. 



The nerve was examined (A) at once, and 1, 2, 3, &c., after succes- 

 sive immersions of ten minutes' duration in a 0*6 gramme per cent. 

 NaCl solution. 



Ohms . . . 



Tolts 



Grammes . . 

 Centimetres 



An error is evidently introduced into the measurement of resistance, 

 if we wish to consider the resistance of a cylinder of the nerve of con- 

 stant length and cross section, by the increase in volume attending 

 the increase of weight. 



Failing an actual determination of the area of the cross section, or 

 one of the volume from which it might be directly obtained by 

 dividing by the length, the value of the weight found in grammes has 

 been treated as volume in cubic centimetres, and used in this way. 

 The error introduced by a neglect of the specific gravity is not, in the 

 case considered, appreciable. 



The " specific resistances " for unit length and cross section found in 

 this way from the figures given are 



A. 

 165 



(1.) 

 184 



(2.) (3.) (4.) (5.) 



180 182 | 184 | 188 ohms. 



Experiment B. Sciatic Nerve of Oat, 



The experiment was in every way similar to the last, with the single 

 exception that the solution used was an NaCl solution of 0'75 gramme 

 per cent. 



