GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 



97 



change and non-conducting area; 1 or the nerve-ends ^ere poisoned with 

 curare (see p. 41), and the nerve excited until the effect of the drug wore off, 

 and the nerve-impulse was able to reach the muscle ; 2 or the part of the nerve 

 near the muscle was temporarily deprived of its conducting power by an 

 anaesthetic, such as ether. Another method of experimentation consisted in 

 using the negative variation current of a nerve (see p. 140) as an indication 

 of its activity, the presence of the current being observed with the galvanom- 

 eter. 3 Other experimenters have examined the vagus nerve, to see if after 

 long-continued stimulation it was still capable of inhibiting the heart, the 

 effect of the stimulation being prevented from acting on the heart muscle 

 during the experiment by atropin, 4 or by cold, applied locally to the nerve. 5 

 Still another method was to study the effect of long-continued stimulation on 

 the secretory fibres of the chorda tympani, the exciting impulse being kept 

 from the gland-cells by atropin. 6 Most of these experiments have yielded nega- 

 tive results, and it is doubtful whether nerves are fatigued by the process of 

 conduction. 



These results, of course, do not show that the nerve-fibres can live and 

 function independently of chemical changes. As has been said, nerves lose their 

 irritability in time if deprived of the normal blood-supply, and undoubtedly 

 they are, like all protoplasmic structures, continually the seat of metabolic 

 processes. The normal function of the nerve, however, the conduction of the 

 nerve-impulse, seems to take place without any marked chemical change. 



Nature of the Conduction Process. There have been a great many 

 views as to the nature of the conduction process, one after the other being 

 advanced and combated as physiological facts bearing on the question have 

 been accumulated. It has been suggested that the whole nerve moved like a 

 bell-rope; that the nerve was a tube, and that a biting acid flowed along it; 

 that the nerve contained an elastic fluid which was thrown into oscillations ; 

 that it conducted an electric current, like a wire ; that it was composed of 

 definitely arranged electro-motor molecules which exerted an electro-dynamic 

 effect on each other ; that it was made up of chemical particles, which like 

 the particles of powder in a fuse, underwent an explosive change, each in 

 turn exciting its neighbor ; that the irritant caused a chemical change, which 

 produced an alteration of the electrical condition of such a nature as to excite 

 neighboring parts to chemical change and thereby to electrical change, and 

 so alternating chemical and electrical changes progressed along the fibre in the 

 form of a wave ; finally, that the molecules of the nerve-substance underwent 

 a form of physical vibration analogous to that assumed for light. 



1 Bernstein : Pfluger's Archiv, 1877, xv. p. 289. Wedenski : Centralblatt fur die medicinischen 

 Wissenschaften, 1884. 



2 Bowditch : Journal of Physiology, 1885, vi. p. 133. 



3 Wedenski : loc. cit. Maschek : Sitzungsberichte der Wiener Academic, 1887, Bd. xcv. Ahthl. 3. 

 * Szana : Archiv fur Anatomie und Physiologic, 1891, p. 315. 



5 Howell, Budgett, and Leonard : Journal of Physiology, 1894, xvi. p. 312. 



6 Lambert : Comptes-rendus de la Societe de Biologie, 1894, p. 511. 



7 



