THORACOCENTESIS 53 



be possible, as the outlines of the ribs can not be accurately 

 traced in that part of the thorax, except in emaciated animals. 

 In this "event, the spot is determined by tracing a rib as far 

 as possible and. then making a mental calculation of its course 

 beneath the flesh. 



Second Step.— Disinfecting the Field and Instrument. — 

 The point selected is clipped and shaved and then well 

 washed with mercuric chloride solution 1-500. The canula 

 is passed frough the flame of a candle, match or gas-jet. 



Third Step. — Inserting the Trocar and Canula.— The 

 operator stands behind the field, holds the instrument in the 

 right hand (Fig. 27) and then slowly and deliberately pushes 

 it, into the thorax, in an oblique direction, inward, forward 

 and upward. This oblique direction of the canula, is one of 

 the salient features of the operation, in that it prevents strik- 

 ing a rib. Ribs are so arranged as to almost over-lap one 

 another roof-like, from before backward. If attacked from 

 behind an object easily finds the space between them, but if 

 attacked from in front the space could hardly be entered at 

 all. 



Fourth Step. — Aspirating the Contents. — When the in- 

 strument has penetrated safely through the wall, the trocar 

 is removed from the canula and the fluid allowed to flow into 

 a pail previously provided for the purpose. The canula is 

 immobilized with the fingers ; otherwise it will move about 

 with the respiratory movements. As long as the stream is 

 free and keeps the canula full, it is allowed to flow without 

 further ceremony. Later, however, the flow will spurt only 

 during the inspiration, and .between the spurts, air will be 

 aspirated into the thorax to the decided detriment of the pa- 

 tient. To prevent this occurrence a rubber tube is attached 

 to the end of the canula and dropped into the pail which now 

 contains a quantity of the liquid. With one end of the rub- 

 ber tubing attached to the canula and the other buried under 

 the fluid in the pail, the admission of air into the th©rax is 

 effectually blocked and the aspiration will continue until all 

 of the contents has flowed out. The author sometimes uses 

 a bottle which is hung by its neck to the surcingle, the tube is 

 dropped into it and the aspiration allowed to go on unat- 

 tended for hours. (Fig. 25.) 



Fifth Step. — Protecting the Wound.— Although the 

 abrasion is a small one, and the chance of infection ab extra 

 is slight, it is nevertheless sensible to clothe the breach with 

 an impervious dressing, such as collodion, tar, vaseline, etc, 



