xvi] 



ANAESTHETICS HUMANE DESTRUCTION 



193 



often have I seen neurectomy, quittor and 

 operations for seton, removal of tumours, etc., 

 castration, straightening of crooked tails (see 

 Sec. 650), etc., performed without the use of 

 even a local anaesthetic ! It is a cowardly prac- 

 tice and foolish to dispense with such aid, 

 because there is no need to rope a horse down 

 as if he were a ravaging lion. With local 

 anaesthetics nearly all of the above operations 

 can be performed without the use of a single 

 rope and without the horse feeling pain. 



754. The methods of producing local anaes- 

 thesia are : (1) freezing the part ; (2) injecting a 

 drug that temporarily kills the nerve ; (3) by 

 local application of fluids, or by rubbing these 

 in ; and (4) by electricity. 



For the first method, a'n ether spray and 

 ethyl chloride are used. 



For the second, cocaine, eucaine, quinine and 

 urea hydrochloride, stovaine, and anaesthaine 

 are used. 



For the third, any of the above solutions are 

 poured on to the part for instance, into the eye. 



For the fourth, a series of electrical impulses 

 are produced upon the part. 



755. Local Anesthesia by Freezing. If a 

 very slight local anaesthesia is required, ethyl 

 chloride is merely poured on to the part drop 

 by drop, but for deeper effects the ether spray 

 must be used. The principle is this : an 

 Apparatus that produces a very fine spray of 

 ether (similar to the bottle barbers use to spray 

 the face) is used. When a liquid is forced 

 through the air in a fine spray it will evaporate 

 (turn into vapour). When a liquid is trans- 

 formed into vapour, heat is required to cause 

 this transformation. Thus, if a liquid in contact 

 with another body is changed into a vapour, the 

 heat that it requires for this is taken from the 

 body with which it is in contact. For example, 

 one's hand, if wetted and held in the wind, 

 becomes cold, due to the evaporation of the 

 water taking heat from the hand. 



This reduction in heat is very great, as it 

 requires 536 times as much heat to change one 

 volume of water at 212 F. into steam at the 

 same temperature as it does to raise that volume 

 of water, say, from 211 to 212. The figure 536 

 is called the latent heat of steam or water vapour. 



Very volatile liquids, as ether, by evaporating 

 at a very low temperature about 84 F. (less 

 than blood heat) produce a very much greater 

 reduction in temperature. If ether is sprayed on 

 to a part of the body, in a few minutes that part 

 becomes frozen and insensitive to pain. Of 

 course, the freezing is quite local. 



756. Method of Using Ether Spray. For 

 veterinary use the methyl ether is generally 

 used, as it is much cheaper than the ethyl 

 ether. The part is clipped free of hair. If only 

 a cut is to be made in the skin, as in inserting 

 a seton needle, the part is sprayed in the direc- 



tion of the needle until the tissues become quite 

 hard and the skin appears a peculiar blue colour. 

 The incision is then made with the seton scissors, 

 and the spray brought upon the incision for a 

 minute. The needle is inserted, and the spray 

 again played over the skin ahead of the point of 

 the needle. The seton thread is greased with an 

 antiseptic, so that when it is drawn through it 

 will cause no pain. 



Other small cuts are made in the same way. 

 In removing a tumour that is on the surface, 

 the same procedure is resorted to, the spray 

 being kept well round and over the part to be 

 cut and well into each incision as it is made, 

 the knife being only inserted a little way, with- 

 drawn, and the spray injected, and so on. No 

 part must be cut unless it is quite hard, show- 

 ing that there is no feeling. It requires con- 

 siderable skill to operate successfully in this 

 way, and if done properly there will be no pain 

 felt. In large tumours more than one spray will 

 be necessary to keep the part insensitive. 



757. For firing the same is done. Large 

 patches six inches square have been fired by deep 

 line firing without the horse having his legs tied 

 at all and without his feeling any pain. In 

 using the spray for firing, only the skin is frozen, 

 i.e. the anaesthetising must not be done too 

 deeply, as the cooling effect on the iron will be 

 too great. The local anaesthetic also prevents the 

 after-pain considerably, which, by the way, ia 

 the most painful part of firing. 



For applying caustics and escharotics, the 

 ether spray should be used as above, thus remov- 

 ing all pain. 



758. For nerving, the ether spray is of the 

 greatest use. The operation of cutting a nerve 

 (e.g. the common operation of radial neurec- 

 tomy) in the horse is an extremely painful one, 

 yet how often is a local anaesthetic used? The 

 incision is made, as above explained, right over 

 the nerve. There will be no bleeding, because 

 everything will be frozen. The spray is kept on 

 until the tissues around the nerve are quite hard. 

 The nerve is then exposed, and made free from 

 connective tissue underneath ; the spray is then 

 kept on until the nerve becomes almost like 

 metal. The nerve is cut an inch should be 

 taken out and the wound dressed in the usual 

 manner. Sewing up is not advisable. 



Ether spray is also used to detect lameness. 

 For example, a certain joint, as the knee, is sus- 

 pected of lameness ; it is made insensible, and 

 if the lameness disappears it is clear that it was 

 the knee that caused the trouble. 



Internal operations, such as removal of an 

 obstruction in the caecum, or the passage of the 

 foetus through the side of the womb when 

 normal delivery through the pelvis is impossible, 

 have been carried out with success with the aid 

 of the ether spray when used very carefully, so 

 that no part was cut unless hardened. 



