300 INOEGANIC AGENTS 



first stage of anaesthesia. A subdivision of the first stage, 

 sometimes described as the anodyne stage, occurs when 

 sensation is lost, before consciousness and voluntary 

 motion. Short operations, as extraction of teeth, have been 

 done by men upon themselves in the anodyne stage of anaes- 

 thesia, vyithout pain. The anaesthetic stage is that condition 

 characterized by absence of consciousness, sensation, motion, 

 and partial loss of reflex action, and is that state suitable 

 for operations. The stimulating action of the anfesthetic 

 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 com- 

 pletely relaxed, and the patient lies absolutely motionless. 

 The conjunctivse fail to respond to irritation, i.e., winking is 

 not produced when the conjunctival membrane 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 anjesthetie 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 faeces 

 are passed involuntarily. Micturition frequently occurs in 

 the first stages of anaesthesia and should not of itself be con- 

 sidered 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 intervals intervening between them. The 

 pupils are often dilated. The pupil is 'said to be a guide 

 during ansesthesia, especially with chloroform, since it is 

 contracted during the ansesthetic stage and dilates quickly 

 when danger appi-oaches. 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. 



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