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AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



up by small stimuli from the spinal cord is shown by the fact that if the nerves 

 be severed, or the nerve-ends be poisoned by curare, the muscle absorbs less 

 oxygen and gives off less carbon dioxide than when at rest under normal 

 conditions. 1 



The theory of a reflex chemical tonus independent of contraction implies 

 the existence of special nervous mechanisms for the exciting of chemical 

 changes in the muscles which shall result in the liberation of energy as heat, 

 independent of the change of form of the muscle. The question of the exist- 

 ence of special nervous mechanisms controlling heat-production — heat-centres, 

 as they are called — will be considered in another part of this book. 



E. Electrical Phenomena in Muscle and Nerve. 2 



The active muscle liberates three forms of energy : mechanical work, heat, 

 and electricity. The active nerve makes no visible movements, gives off no 



recognizable quantity of heat, but 

 exhibits changes in electrical condition 

 quite comparable to those observed in 

 the active muscle. The electrical 

 changes in nerves are the only evidence 

 of activity which we can observe, aside 

 from the effect of the nerve on the 

 organ which it excites ; they are there- 

 fore of great interest to us. ' 



Electrical energy, like all forms of 

 active energy, is the result of a trans- 

 formation of potential or some form of 

 kinetic energy. In the case of the 

 muscle, as of an electric battery, we 

 find electricity to be associated with 

 chemical change, and believe it to be 

 liberated from stored potential energy. 

 In the case of nerves no chemical 

 change can be detected during action, 

 and hence we are at a loss to explain 

 the development of electricity. We 

 can only say that it is the result of 

 some chemical or physical process 

 which we have as yet failed to discover. 

 Although activity of nerve and 

 muscle is found to be associated with electrical change, we must not suppose 

 functional activity to be in any sense an electrical process. The movements 



1 Zimtz: Pjlii'in-'s Archiv, 1876, xii. 522; Colasanti, Ibid., 1878, xvi. S. 57. 

 3 Biedermann : Electrophysiologic, Jena, 1895, Bd. ii.; translation by F. A. Wei by, 1898; 

 Waller: Lectures on Animal Electricity, London, 1897. 



Fig. 02.— Schema of galvanometer: n, .s, north 

 and south poles >>f astatic pair of magnets; m, 

 compensating magnet, held by friction on the 

 staff, and capable of being approached to, or ro- 

 tated with reference to, the suspended magnet ; 



, mirror ;/, fibre supporting the magnets; e,c, 

 c, c, coils of wire to carry the electric current 

 near to the magnets, the upper coils being wound 

 in the opposite direction to the lower; e, i , imn 

 polarizablc electrodes applied to the longitudinal 

 surface and cross section of a muscle. 



