52 OPERATIVE TECHNIQUE. 



calls for similar precaution. Rattling in the throat, a serious symptom 

 in man, is of less importance in horses. In the event of its occurring, 

 the tongue should be grasped and drawn forward. Even then the 

 noise does not always cease, being probably due to vibration of 

 the relaxed soft palate, which is set in motion by the stream of 

 air passing through the mouth during respiration. 



The loss of sensibility, muscular weakness, character of the pulse 

 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 anaes- 

 thesia. 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 intoxication. 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 anaes- 

 thesia becomes pronounced, the pupil, dilated during the period of excite- 

 ment, contracts. During anaesthesia it remains contracted and immobile, 

 dilating slowly as sensibility returns. Rapid dilatation at an advanced 

 stage of anaesthesia is a sign of bulbar intoxication and of imminent 

 syncope. 



When the corneal reflex is lost and the pupil contracted, sensibility 

 has disappeared, and muscular relaxation is complete. Provided 

 respiration and circulation continue regular, anaesthesia can then 

 be prolonged for periods of two or even three hours without danger by 

 occasionally administering further small doses of chloroform. 



On completion of the operation the hobbles are removed ; but 

 the horse is left undisturbed until it rises of itself, which will usually 

 happen in a quarter to half an hour. Should the animal be forced 

 to rise before consciousness has entirely returned, it walks unsteadily, 

 " bores" forward like an animal with brain disease, and may fall. To 

 support it an assistant may walk on each side, with a hand on the 

 point of the hip, and one behind holding the tail. 



Administered with the foregoing precautions chloroform becomes 



