degive's and graillot's cauteries. 



159 



from the handle. At its upper part is a clamping nut, by means of 

 which the head can be set in a line with, or at any angle to, the stem. 



The head consists of a hollow nickel 

 shell carrying at its extremity the cauter- 

 ising surface or point, made of platinum- 

 iridium alloy, and lined within by frag- 

 ments of fine platinum gauze to assist 

 the combustion of the vapours. Special 

 attention is directed to the screw (d) 

 shown on each of the heads, as it plays 

 an important part in the working of the 

 apparatus. 



To start the cautery in action, the 

 stem is first unscrewed, and benzoline 

 poured into the handle from the upper 

 end until it overflows. The handle is 

 then inverted, and all excess of benzoline 

 allowed to flow away, leaving the sponge 

 saturated. The parts are then screwed 

 together, the bellows affixed and started, 

 the little two-way stopcock (a) at the 

 bottom turned nearly at right angles, 

 the small screw (d) in the head opened 

 as far as possible, and a light applied 

 to the holes shown in the head. If all 

 is acting properly, a strong bluish flame 

 will be seen within the head, and a rather 

 loud hissing sound will be heard. If not, 

 the bottom stopcock is turned one way 

 or the other, so as to alter the pro- 

 portions of air and benzoline vapour 

 passing to the head, until the flame 

 appears and burns steadily. In a minute 

 or two the entire head will become 

 strongly heated, and if the top screw 

 (in the head) be then turned home, the 

 blue flame will disappear, the hissing 

 noise will cease, and the point of the 

 cautery, previously quite dull, will sud- 

 denly begin to glow, and soon attain a 



bright reddish-white heat. The reason of this is that the direct 

 flame is extinguished, and the vapours are caused to burn within 



The zoo-cauterv. 



