266 Dr. H. H. Alcock. On the Negative Variation [Jan. 17.. 



Young Eabbit. 

 Nerves kept for 3 7i circa post-mortem. 



Experi- 

 ment No. 



Temp, of 

 nerve. 



Yolt. of 

 neg. var. 

 at excit. 

 100. 



Volt, of 

 neg. var. 

 at exeit. 

 30. 



Notes. 





30° C. 



-00033 



-00023 



1 -05 p. c. NaCl + 



*5 p. c. maltose. 

 R. sciatic. 



B t(1 



30° C. 



-00023 



-00016 



1-05 p. c. NaClonk. 

 L. sciatic. 



The two nerves of opposite sides are here compared, and the com- 

 parison is in favour of the E. sciatic which had been treated with 

 maltose. No account is here possible of the precautions used to- 

 exclude fallacy, but many further experiments support the one quoted, 

 and it is at least very probable that the maltose is the active variant. 



The method employed for determining the negative variation and 

 the action of anaesthetics was in all cases that of Waller. An addi- 

 tional larger box was used, with a false bottom of wood, on which the 

 nerve chamber rested. Below this was a layer of water, so that the 

 nerve was kept in an atmosphere nearly saturated with water vapour 

 at whatever temperature was desired. 



The standard " Berne " coil, worked with two Leclanche cells, was 

 used to give the excitation, which always consisted of tetanising shocks 

 for a period of 13 seconds, repeated once a minute. The number of 

 units used was 500, when not otherwise stated. The usual precautions 

 against current escape and electrotonus were carefully observed; this 

 was found to be particularly necessary in the case of bird's nerve. 



Half-grown rabbits were found very suitable animals to use, as the 

 small amount of connective tissues permitted the nerves to be dissected 

 out with a minimal amount of injury. Experiments were also made 

 with cats, kittens, guinea-pigs, hedgehogs, pigeons, and frogs. The 

 technique is considerably easier in the case of young animals ; adults, 

 however, answer well if care be taken. In the latter, and especially 

 in the nerves of birds, it is advisable to work at rather higher tem- 

 peratures than those given above. 



Voltage and Strength of Excitation. 



The voltage of the negative variation varies with the animal, the 

 nerve employed, the temperature and condition of the nerve, and,, 

 within certain limits, with the strength of excitation. 



