44 ANAESTHESIA IN THE HORSE. 



small closes of the agent employed ; larger amounts are dangerous, 

 as being liable to induce the third stage of anaesthesia, viz. collapse 

 or intoxication. This is characterised by progressive retardation 

 of respiration and circulation, and by sudden dilatation of the pupil. 

 Respiratory movements become superficial and cease for compara- 

 tively long periods ; the heart's action diminishes, the pulse is small, 

 soft, and irregular. Finally the medulla becomes intoxicated, 

 respiration is arrested, the heart ceases to beat, and death occurs 

 by respiratory syncope. 



The phenomena of anaesthesia vary according to whether ether, 

 chloroform, or another anaesthetic is employed. With ether the 

 period of excitement is longer and more pronounced than with 

 chloroform. With certain fixed anaesthetics the phase of excitement 

 is suppressed or little marked. Although the exact action of chloral 

 is still open to discussion, it is known to produce immediate and 

 profound anaesthesia without preliminary disturbance when adminis- 

 tered intra-venously. On the other hand, salts of morphine some- 

 times produce lively excitement prolonged for some hours. The 

 difference, however, interests physiologists more than practitioners. 

 The chief point for the latter is the degree of toxicity of these agents. 

 i.e. the danger attending their use. No general anaesthetic is without 

 danger, and even in veterinary surgery, where the employment of 

 anaesthesia is limited, every practitioner has probably had a fatal 



ANAESTHESIA IN THE HORSE. 



Chloroform probably produces the most rapid and complete 

 anaesthesia in the horse. It is not so dangerous for solipeds as lias 

 been suggested. The writer, whose experience extends to nearly 

 a thousand cases, has only seen two fatal results, which occurred 

 after deep surgical anaesthesia had been maintained, in one case for 

 over two hours, and in the other over three. Needless to say, 

 recovery of consciousness is slow after prolonged operations, and the 

 animals may not rise for half an hour to an hour after their termina- 

 tion, but given reasonable care in administration chloroform fulfils 

 all requirements. 



In company with Dr. Clarke, the writer attempted on several 

 occasions to kill animals by the administration of air saturated at 

 ordinary temperature with chloroform vapour, hut the experiments 

 all proved the extreme difficulty of the attempt. Where, however, 

 the animal is partially asphyxiated, as in using several of the 

 common veterinary inhalers, death can be produced in eight to ten 



