v or MI .-ru-:s AM M:I;\I 



cannot lie shown with mil' present appliances. As 



motions of the smallest particles (molecules) probably 

 take plaee iu the nerve, though the external form 

 remains unaltered, mid therefore no work worthy of 

 consideration is accomplished, it is ea>ilv intelligible 

 that the>e processes may be accompanied only by ex- 

 tremely slight changes in the constituent parts. 



The speed with which death and the changes in 

 excitability connected with death take place mainly 

 depends, apart from the length of the nerve, on the 

 temperature. The higher the temperature the more 

 quickly does the nerve die. At a temperature of 44 C. 

 death occurs in from ten to fifteen minutes; at 75 C. 

 in a few -eeonds; and in the ayerage temperature of a 

 room the lower ends of a long sciatic nerve may re- 

 tain their excitability for twenty-four hours or longer 

 after extraction and preparation. Drying at lir.-t in- 

 creases the excitability, but a fterwards. rapidly deciva.-es 

 it. Chemical agents, such as acids, alkalis and salts, 

 destroy the excitability the more rapidly the more 

 concentrated they are. In distilled water the nerve 

 swells and rapidly becomes incapable of excitement. 

 There are, therefore, certain densities of salt solutions 

 in \\hich the nerve remains excitable longer than in 

 thinner or in more dense solutions. A solnt ion of com- 

 mon salt of 0-6 to 1 per Cent., for instance, has almost 



llo effect on ;i l|er\e submerged ill it, and preserves the 



excitability of this nerve about a- long as damp air. 

 I'ui'e olive oil, if not acid, may al-o be reganled as 

 innocuous. These are, therefore, u-, d when the in- 

 Iliiciiee of different temperatures on the nerve is to he- 

 studied. 



