100 T. J. ENGLISH ON A PNEUMATIC INJECTING APPARATUS. 



its centre, and over it is fastened, by means of heat, a small, tliin, 

 flat piece of ivory, made from a vaccine point, a little longer than 

 broad (G in figs. iii. and iv.), also having a hole in its centre ; this 

 piece of ivory forms the basis or rest for the oil silk valve (H in 

 figs. iii. and iv.) which is of the same shape, but a little smaller, 

 and is retained in its place by sealing-wax varnish at one margin 

 only. A coating of varnish is then carried over the gutta-percha 

 and lower part of the glass tube, to stop all escape of air at the 

 junction of the two, care being taken to keep the ivory plate free 

 from it. 



The 3rd neck is closed by a cork, packed with wash leather, and 

 serves for the introduction of the injecting fluid into the bottle. 



To use the instrument the requisite sized nozzle is fixed on the 

 gutta-percha tube, which is closed by the pinch -cock ; about 4oz. 

 of injection are then poured into the bottle through the third neck, 

 and the cork firmly inserted, the leather surrounding it having been 

 previously, wetted ; pressure is now made on the ball B, taking care 

 to place one finger over the hole C, by this means the air is forced 

 down the tube through the valve into the bottle ; on removing the 

 pressure from the ball the valve closes, and the ball is refilled by 

 air entering the small hole C ; after this operation has been done 

 twice the pinch-cock of No. 1 tube is cautiously opened, and the in- 

 jecting fluid, acted on by the condensed air in the bottle, rushes 

 up that tube ; when it completely fills the tube and nozzle, the cock 

 is again closed, and further exit of the fluid restrained. The in- 

 strument is now ready, and the nozzle is introduced and tied into 

 an artery in the same way as the ordinary syringe. 



I have used glass for the nozzles, preferring that material to 

 metal, not only because they are lighter, but because they can be 

 made very easily, and can be drawn out to the finest size. When the 

 injection requires replenishing, the cock is closed and more fluid 

 poured in at the third neck. 



Such is the instrument in its simplest form, but, if wished, it may 

 have a small manometer attached to it, to indicate the exact 

 pressure employed, although I have generally found that the 

 amount of force required to drive the air out of the ball into the 

 bottle is a sufficient guide. The bottle may be of any capacity, and 

 in choosing one, regard should be had to its strength and freedom 

 from cracks and flaws of any kind ; and when completed, it should be 

 tried with a little water, high pressure being used, to test its capa- 



