"'L'l' Mr. J. S. Macdonald. 



the " normal saline " in just such a way as to cause exactly the 

 variations described in the apparent value of the E.M.F., and that 

 the variations would be connected by the simple law found. 



If so, an examination of the alterations taking place in the same 

 " normal solution " when its temperature is varied presents an 

 anomaly for explanation. The solution maintained at anything 

 approaching the temperature of the body, in which the E..M.F. 

 would remain constant, is not 0'70 per cent., but 0'45 per cent. 

 NaCl solution. 



A more striking anomaly still is obtained when an appeal is made 

 to solutions of electrolytes other than NaCl ; an extreme instance is 

 given by the consideration of solutions of NaOH. 



The following data are taken from four separate experiments in 

 which 5 cm. pieces of sciatic nerves (cat), removed immediately after 

 death, were placed in each case in 500 c.c. of an NaOH solution at 

 a temperature of 17 C., and left in it for 25 minutes. 



Solution. E.M.F. " recovered." 



(1) 0-025 gramme per cent. NaOH. 1-620 



(2) 0-050 0-922 



(3) 0-050 ,. 0-800 



(4) 0-100 ? , 0-422 



Proceeding as before, and multiplying the concentration by the 

 E.M.F., we have 



(1) 0-025x1-620 = 0-0405 



(2) 0-050 x 0-922 = 0461 



(3) 0-050 x 0-800 = 0-0400 



(4) 0-100 x 0-422 = 0-0422. 



The concentration law is the same as for NaCl, but the " constant ' 

 solution is 0-04 instead of 0'7. Dividing these figures by the mole- 

 cular weights of NaOH and NaCl respectively, the proportion existing 

 l>etween them is 1 to 12 ; and this, even allowing for the greater con- 

 ductivity of NaOH solutions, is evidently a relation of a more complex 

 kind than that found when passing from one concentration to another 

 .f a solution of the same electrolyte. 



***** 



In certain types of experiments, such as those in which the effect of 

 tap water was studied (vide supra) upon the nerves of animals in a state 

 <>f li'jnr nif/rti*, the capacity of the established hypothesis to explain the 

 facts is strained to an absurd degree. The following are brief descrip- 

 tions of typical experiments concerning which the same statement may 

 safely be made : 



