4 s 



GENERAL AN.ESTHESIA. 



and respiration, variation in the pupil, and the persistence or loss 

 of the corneal reflex indicate the degree of anaesthesia. 



Complete anaesthesia is characterised by disappearance of the 

 oculo-palpebral reflex and contraction of the pupil. At this stage 

 should the conjunctiva or cornea be touched no movement of the 

 eyelids follows, and touching the cornea has therefore become the 

 usual test of anaesthesia. When the corneal reflex ceases inhalation 

 may be stopped, to be resumed with its reappearance. The test 

 is doubly valuable : it shows anaesthesia to be complete, whilst its 

 disappearance is usually long antecedent to the period of intoxica- 



Fig. 65. — Cox's chloroform muzzle. 



Fig. 66. — Arnold's modified Carlisle 

 chloroform muzzle. 



tion. Too much weight, however, cannot be attached to the advice 

 " watch the breathing." The breathing, and not the pulse or any 

 other sign, is the only safe guide in administering an anaesthetic. 

 The abolition of the corneal reflex usually occurs long before respiration 

 is endangered, so that it is a convenient guide ; but its occurrence 

 is subject to irregularity, and it must never be relied on to the exclusion 

 of the breathing. 



Variations in the pupil also afford valuable information. As 

 anaesthesia becomes pronounced, the pupil, dilated dining Hie period 

 of excitement, contracts. During anesthesia it remains contracted 

 and immobile, dilating slowly as sensibility returns. Rapid dila- 



