66 OPERATIVE TECHNIQUE. 



for a month afterwards he showed nothing abnormal. Killed at the 

 end of the month, no trace whatever could be found of the injections. 

 All his organs were perfectly healthy. 



These experiments — as yet not numerous, which the investi- 

 gators intend to pursue — show, nevertheless, in a convincing manner 

 that analgesia produced by cocaine injected into the neural canal is 

 applicable in veterinary surgery, and that, with proper precautions, 

 there is no danger. (It is worthy of note that not one of the subjects 

 of experiment, not even those which had received manifestly too 

 great a dose of cocaine, exhibited any abnormal respiratory or circu- 

 latory symptoms.) The doses used were fifteen to seventy-five minims 

 of a 2 per cent, solution of cocaine for the horse or ox. For dogs 

 fifteen minims should not be exceeded. 



(b) Local Anesthesia. 



The dangers of general anaesthesia have stimulated the search for 

 means of rendering insensitive the region of operation alone. Pro- 

 longed compression of tissues and mediate compression of the nervous 

 trunks supplying the part are very imperfect methods. For a long 

 time ice refrigerating mixtures and ether spray were exclusively used. 

 Cocaine was afterwards discovered, and soon became popular. 



Anesthesia by Cold. — The prolonged action of cold renders 

 superficial tissues bloodless and diminishes or even abolishes sensibility. 

 Refrigerant mixtures have been used in operations like neurectomy. 



Crushed ice and salt, mixed in the proportion of 2 to i are packed 

 into a long bag and applied to the region of operation. In a few 

 minutes, especially if the bag is pressed firmly into contact with the 

 part, the skin becomes cold, firm, and insensitive, and incisions unless 

 deep neither provoke pain nor haemorrhage. The anaesthesia, however, 

 is of short duration, and operation must be rapid. 



By projecting an ether spray on the parts the temperature is soon 

 so far reduced that trifling operations may be performed without pain. 

 The action is rendered more rapid and complete by previously apply- 

 ing an Esmarch bandage. It is difficult, however, to render inflamed 

 parts insensitive, and for this purpose refrigerating mixtures are pre- 

 ferable. 



Bisulphide of carbon has no advantage over ether. 



Methyl bichloride and anestile, successfully used in man for trouble- 

 some neuralgia, are almost too active, and though rendering the skin 

 insensitive in a few seconds not infrequently freeze it, causing more or 

 less extensive necrosis. 



Local Anesthesia by Cocaine. — Cocaine is almost insoluble in 

 water, but the greater number of its salts dissolve freely. The most 



