226 



INORGANIC AGENTS 



of the anesthetic has ceased and there is now depression of the cerebral 

 functions, the motor and sensory tract of the cord, and, to a partial 

 extent, the' reflex centres. The muscles are completely relaxed, and 

 the patient lies absolutely motionless. The conjunctivsB fail to respond 

 to irritation, i. e., winking is not produced when the conjunctival mem- 

 brane is lightly touched with the finger. Occasionally the muscles are 

 seen to be rigid and twitching during this stage of etherization, although 

 sensation and consciousness are absent. The respiration and pulse should 

 not be particularly altered during the anesthetic stage, unless danger 

 threatens. In the last stage, narcosis, or poisoning, is beginning, and 

 there is depression of the three great medullary centres controlling the 

 heart, respiration and vascular tension, and also the lowest reflex centres 

 of the cord, so that the urine and feces are passed involuntarily. Mic- 

 turition frequently occurs in the first stages of anesthesia and should 

 not of itself be considered a danger signal. The pulse becomes rapid, 

 feeble and irregular; the breathing is at first stertorous, and then the 

 respiratory movements become shallow and weak, with considerable in- 

 tervals intervening between them. The pupils are often dilated. The 

 pupil is said to be a guide during anesthesia, especially with chloroform, 

 since it is contracted during the anesthetic stage and dilates quickly 

 when danger approaches. Death, however, occurs in animals with either 

 dilated or contracted pupils. With the former, probably from asphyxia; 

 with the latter, from syncope; and the pupil should not be regarded as 

 an unfailing sign. The foregoing stages are conventional, and are not 

 in any case so clearly defined in practice as they are described theoreti- 

 cally upon paper. The first stage may be either absent or prolonged, 

 and the last stage should not be reached at all. 



Comparison of Ether With Chloroform. 



ETHER. 



More diffusible. 



Inflammable. 



Irritating, may induce bronchitis, pul- 

 monary edema and pneumonia, unless 

 properly diluted (see drop method, 

 p. 231). 



Reflexly stimulant to heart and vaso- 

 motor centres and does not so easily 

 depress the respiratory centres. 



Larger quantity required. 



More expensive. 

 Less rapid. 



Fatal from respiratory failure and 

 acapnia (see p. 227). 



CHLOROFORM. 



Vapor heavier. 



Non-inflammable. 



Non-irritating. 



Depresses powerfully the heart, respira- 

 tory and vasomotor centres, in large 

 doses. 



Drams of chloroform do the work of 

 ounces of ether. 



Cheaper. 



Acts more quickly; profoundly and 

 persistently. 



Fatal from respiratory failure com- 

 bined with circulatory depression and 

 vasomotor paralysis, or later -from 

 fatty degeneration of the internal or- 

 gans, or from acidosis and acetone 

 poisoning. Occasionally fatality re- 

 sults from reflex Inhibitory arrest of 

 the heart from inhalation of too con- 

 centrated vapor. 



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