THE THEORY OF ANAESTHESIA. 319 



chanical shock may cause temporary loss of irritability. This is 

 probably an effect of over-stimulation and due to prolongation 

 of the refractory period ; it resembles in some respects the effect 

 produced in voluntary muscle by poisons like veratrin, which 

 greatly prolongs the relaxation phase and the recovery of irrita- 

 bility following contraction. The paralysis due to mechanical 

 shock differs however from that of anaesthesia in important 

 respects; it represents an injury from which the cell can recover, 

 while true unmixed anaesthesia is quite without injurious action. 

 Certain effects of altered temperature have a closer resemblance 

 to anaesthesia. Most cells and tissues, within the range of 

 temperature in which they show normal activity, show decreased 

 automatic activity with decrease of temperature. Thus accord- 

 ing to Snyder 1 the heart of the tortoise shows eighteen beats per 

 minute at 20 and thirty-five at 30. Observations on the hearts 

 of other animals have given similar results. 2 Within the physio- 

 logical range of temperature the rate is doubled or trebled by a 

 rise of 10. This rate of change of velocity with temperature, 

 or temperature-coefficient, is characteristic of chemical reactions 

 in general and is not a distinctively physiological phenomenon. 

 Metabolic and hence vital activity is slowed by cooling just as 

 any other chemical process is slowed. The same temperature- 

 coefficient is shown by a large number of physiological processes 

 including cell-division, rate of conduction in nerve, enzyme action 

 and many others. 3 Thus the above effect of cold is dependent 

 simply on a slowing of chemical processes in cells and has in it 

 nothing distinctively vital. It is important, however, to con- 

 sider this effect in relation to the problem of anaesthesia, for a 

 simple decrease in reaction-velocity, due to the presence of anti- 

 catalytic substances, is held by various investigators to be the 

 essential condition of anaesthesia. Decrease in the rate of a 

 physiological process, like the heart beat, or muscular contrac- 

 tion, or the spread of the excitation-wave in nerve, is not how- 



1 University of California Publications, Physiology, 1905, Vol. 2, p. 125. 



Cf. C. D. Snyder, Amer. Journ. Physiol., 1906, Vol. 17, p. 350; Zeitschr. f. allg. 

 Physiol., 1912, Vol. 14, p. 263; Robertson, BIOL. BULL., 1906, Vol. 10, p. 242; 

 C. G. Rogers, Amer. Journ. Physiol., 1911, Vol. 28, p. 81; BIOL. BULL., 1914, 

 Vol. 27, p. 269; Loeb and Ewald, Biochem. Zeitschr., 1910, Vol. 28, p. 340. 



3 For instances cf. Snyder, "Temperature-coefficients of Various Physiological 

 Actions," Amer. Journ. Physiol., 1908, Vol. 22, p. 309. 



