PARACENTESIS. 



103 



on one, the index and middle finger on the other side, the httle finger 

 being used as a support. The point is caused to enter vertically b}' 

 extending the previously bent fingers. In withdrawing the instrument 

 the opening may, if necessar}', be enlarged, Figs. 121, 122. 



In using a bistoury or lancet the handle is held at right angles to 

 the blade. Many persons grasp the blade, only leaving uncovered 

 sufiicient to penetrate to the desired depth : but this method, how- 



FiG. 124. — Trocar ft)r 

 tapping the chest. 



Fig. 125. — -Trocar for 

 tapping bowel. 



Fig. 126. — Trocar for 

 puncture of rumen. 



ever, has the disadvantage that in case of a mistake in regard to the 

 thickness of the tissues to be divided the fingers must be moved, more- 

 over the operator runs considerable risk of wounding himself. The 

 surgeon should possess sufficient delicacy of touch to know when 

 opposition ceases, that is when the cavity is entered. Supporting the 

 instrument with the fingers in the method described assists in this 

 respect. 



