652 sroiiADic diseases. 



means of an instrument, consisting of a trocar and cannula, 

 guarded by a tap, by which a small quantity of the fluid is with- 

 drawn, the exact nature of which can be identified. If fluid 

 be present it can be withdrawn, an elastic pipe being attached 

 to the tap, and the serum allowed to flow into water. Should 

 the fluid be purulent or too thick to flow through the cannula, 

 a suction syringe is to be applied, the force of which is to be 

 sufficiently strong to cause its evacuation. 



Dr. Bowditch's rules for performing this operation are as 

 follows : — " Find the inferior limit of the sound lung behind, 

 and tap two inches higher than this on the pleuritic side, at a 

 point in a line let fall perpendicularly from the angle of the 

 scapula. Push in the intercostal space here with the point of 

 the finger, and plunge tlie trocar quickly in at the depressed part ; 

 be sure to puncture rapidly, and to a sufficient depth, as you 

 may be balked by the false membranes occluding the cannula. 



" It will sometimes hapf)en that with the greatest care and 

 trouble we are unable to get a fiow of fluid at the part where 

 we first puncture ; it is then our duty to try elsewhere, for our 

 failing may be owing to unusual thickness of the false mem- 

 branes in the lowest inch or two of the pleural cavity. We 

 thereupon repeat the puncture a little higher up, and furtlier 

 towards the axillary line, and here we perhaps find fluid ; at any 

 rate no harm has been done by the two punctures. 



" The circumstances under which paracentesis ought to be 

 performed for pleurisy are the following : — 



" 1st. In all cases of pleurisy, at whatever date, where the fluid 

 is so copious as to fill one pleura, and begins to compress the lung 

 of the other side ; for in all such cases there is the possibility of 

 sudden and fatal orthopncea. 



" 2d. In all cases of double pleurisy, when the total fluid may 

 be said to occupy a space equal to half the united dimensions of 

 the two pleural cavities. 



" 3d. In all cases where, the effusion being large, there have 

 been one or more fits of orthopncea. 



" 4:th. In all cases where the contained fluid can be suspected 

 to be pus, an exploratory puncture must be made ; if purulent, 

 the fluid must be let out. 



" 5ih. In all cases where a pleuritic effusion occupying as much 

 as half of one pleural cavity has existed so long as one month, 

 and shows no sign of progressive absorption," 



