i62 HEATING CAUTERIES. 



continue for another quarter of an hour, a sufficient period to finish 

 an ordinary operation. 



As the whole apparatus would otherwise become unpleasantly 

 warm, the main body of the reservoir is covered with a tube of 

 insulating material, — " vulcanised fibre." The fact that the expen- 

 sive platinum heads and points are entirely dispensed with permits 

 of the apparatus being sold at a very reasonable sum. 



For heating the ordinary iron a forge or small stove is usually 

 employed. Charcoal or coke is preferable to coal. Within recent 

 years, however, advantage has been taken of the numerous automatic 

 lamps, burning petroleum spirit or benzole, to produce a convenient 

 and easily transported stove. In these lamps the pressure produced 

 within the body of the lamp by warming the fluid, causes a small 

 quantity to mount through a capillary tube into a chamber sur- 

 rounding the flame, which chamber is therefore always at a high 

 temperature. Arrived here the liquid is rapidly transformed into 

 gas, and escaping through a small hole, emerges in the form of a 

 powerful jet which sucks air through orifices surrounding it, and 

 when ignited burns with a very intense flame. By adapting to such 

 a lamp a suitable hood for receiving the heads of the firing irons 

 an excellent portable furnace is produced. 



A very good form of automatic petroleum furnace is that shown 

 in Fig. 217. The reservoir (a) contains ordinary petroleum oil, with 

 which it is filled through the plug (6). To set the apparatus in action, 

 the small air-pump (c) is worked for a minute or two, until the air 

 pressure in the reservoir is sufficient to force the oil up to the burner 

 (/). A little methylated spirit is then poured into the ring at the 

 base of the burner and ignited, thus heating the burner. On then 

 cautiously relaxing the screw (0), a fine stream of petroleum flows 

 into the burner, becomes vaporised, and issues as a powerful jet 

 from a small orifice at the base of the tube (/), shown as a dotted 

 line. This jet aspirates strong currents of air through the holes 

 in the burner, mixes with this air, and burns with an intensely hot 

 blue flame within the hood (g). 



Whatever the method of firing adopted, certain general principles 

 must be observed. The preparation of the animal is important. If 

 casting is necessary it should preferably be done on an empty 

 stomach ; if the animal is very vigorous and plethoric, the food 

 allowance should be reduced during the previous days, and laxatives 

 must be administered. The point of operation must be thoroughly 

 cleansed, and the hair cut either with a machine or with scissors, 

 but in deep firing, involving synovial membranes, antiseptic pre- 



