ANESTHESIA BY CHLORAL. 



53 



point of operation must be thoroughly disinfected, and all instru- 

 ments should be sterilised. Everything being ready, an assistant 

 compresses the vein low down in the jugular furrow ; the operator 

 then draws the skin in the direction of the head with one hand, 

 while with the other he thrusts a needle or fine trocar into the 

 distended vessel, taking a very oblique course from above down- 

 wards, i.e., almost parallel with the vessel. Humbert recommends 

 operating in two stages, first dividing the skin, then, after having 

 raised the vein, introducing the needle or trocar. When the opera- 

 tion is done standing he chooses by preference the right jugular. 

 The discharge of a jet of blood through the cannula when the trocar 

 is withdrawn shows that the vein has been penetrated. An assistant 

 holds the cannula firmly, and inclined towards the general line of 

 the neck. The operator next introduces into the opening of the 

 cannula a special metal plug comiected to a rubber tube, which slips 

 over the nozzle of the injecting syringe, and opening the tap injects 

 the necessary quantity of chloral solution ; needless to say, great 

 care must be taken not to inject air. The operation concluded, 

 he frees the cannula from the rubber tube, allows a little blood to 

 escape, and quickly removes the cannula, supporting the skin mean- 

 while with the fingers of the left hand. Colin gives the dose as two 

 and a half to three and a half drachms ; Arloing three to six 

 drachms ; and Nocard one and a quarter drachms per hundred 

 pounds of body-weight. Anaesthesia appears almost immediately. 

 It is more or less profound, and continues for a greater or less time 

 according to the amount of chloral injected. In a few seconds the 

 animal is asleep, the muscles are completely relaxed, the mucous 

 membranes slightly cyanotic, and the respiration and circulation, 

 though disturbed for a moment, rapidly recover their normal rhythm. 

 The animal recovers slowly, remaining stupefied for a time, and 

 sometimes suffering from general trembling of the body muscles. 

 At the end of half an hour to two hours the horse rises, resting for 

 a time on its haunches. Movement of the hind limbs is irregular 

 and uncertain. This weakness sometimes persists for one or two 

 hours. 



When the dose has been too large, or the subject is specially 

 susceptible to the action of chloral, the sleep is very deep, the mucous 

 membranes become darker and darker in colour, the pupil dilates, 

 respiration and circulation become slower and slower, the tempera- 

 ture falls, and death may result. 



If the operation be not performed antiseptically, if the opposite 

 coat of the vein be injured when introducing the cannula, or if the 



