DEGIVE'S AND GRAILLOT'S CAUTERIES. 



121 



corrugated, both to afford a better grip and to increase the surface from 

 which evaporation takes place. Its interior is packed with fragments of 

 sponge saturated with benzohne, and through the centre passes a small 

 tube, which conveys a portion of the air 

 pumped into the apparatus directly to- 

 wards the stem, without passing through 

 the sponge. At the extreme end of the 

 handle is a nipple, over which is slipped 

 the india-rubber tube of the bellows, and a 

 little two-way stopcock (a), which when 

 turned in a line with the handle allows 

 air to pass freely both through the small 

 (direct) tube mentioned, and also through 

 the mass of sponge in the handle ; but 

 when turned at an angle gradually shuts 

 off the stream from the sponge-packed 

 part until at last (at right angles) it admits 

 air alone through the direct tube. By 

 examining the top of the handle before 

 screwing in the stem the small direct air- 

 tube will be seen projecting upwards 

 through the mass of sponge. 



The stem (c) is merely a strong metallic 

 tube supporting the head, and conveying 

 to it the mixed air and benzoline vapour 

 delivered 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 b}' 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 pla3'S 

 an important part in the working of the 



apparatus. Fig. 149.— The zoo-cavitery. 



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 



