DISSECTIONS. 



141 



Fig. 176.— Various Forms of Trocars. 



To puncture with the trocar, the operator will assure himself 

 that it is in good condition, and that the rod can readily be with- 

 drawn from the canula when necessary. Holding the instrument 

 in such a manner that the handle, grasped by the three fingers, 

 rests in the j^alm of the hand, the thumb is applied on the canula 

 near its point of union with the handle, and the index extended on 

 the outside of it, to limit the play of the instrument ; the trocar is 

 pushed through the tissues in a perpendicular direction, and until 

 a sensation of resistance is no longer felt. "When introduced, the 

 canula is held in place with one hand, while with the other the 

 rod is slowly drawn straight out, or by a slight rotary motion. 



If the design of the operation has been the evacuation of the 

 liquid contents of a tumor, as the fluid escapes the growth dimin- 

 ishes, and it becomes necessary to insert the canula further in the 

 ca\ity or turn it in different directions, to ensure the removal of the 

 entire contents. Yet it is necessary to be careful not to press the 

 orifice of the canula against the waUs of the sac, a condition likely 

 to prevent the escape of the fluid. 



To remove the canula, moderate pressure is applied with one 

 hand on the skin around the seat of the puncture, while the other 



