246 
PUNCTURE OF THE THORAX. 
distance varies according to the thickness of the thoracic wall, and in 
the larger animals varies' from 1^ to 2J inches. Should the skin be 
movable on the sublying tissues, it may be pulled forward, and the 
trochar introduced perpendicularly to the chest-wall until the index 
finger meets the skin. The stilette is now withdrawn with the right 
hand, whilst the left supports the canula, and the left index finger is 
held ready to close the opening against entrance of air, which may occur 
Fig. 119.—Dieulafoy’s aspirator, with handle for introducing the needle and 
flexible connection for syringe. 
when the flow of fluid ceases, when inspirations are specially deep, or when 
coughing ensues. If the discharge of fluid is prematurely checked by 
clots of lymph or blood, or by apposition of the lung, a few slight lateral 
movements should be made with the canula, and the stilette or a carefully- 
disinfected probe passed through it. To facilitate the discharge of fluid 
and prevent access of air, various arrangements have been proposed. 
Schuh has devised a trochar, carrying at its outer end a reservoir 
(trough or bath), so that the opening of the canula is always immersed 
in fluid; but this arrangement is not reliable, and is little used. The 
