DISSECTIONS. 



139 



examine the contents of natural cavities, or to provide for the escape 

 of gases or fluids. It is, therefore, a solution of continuity of 

 smaU dimensions, constituting often the first steps of an incision, 

 but which forms also an essential operation. It can be performed 

 with various instruments, as the lancet, the straight bistouiy, the 

 trocar, the exploring needle and then- adjuncts, the aspirator, and 

 the actual cautery. 



Fig. 173. — Various Shapes of Lancets. 



Puncture with the Lancet. — In form and shape the lancet 

 greatly varies, but in general it may be considered as a compound 

 bistoury, with a pointed and two-edged blade. The poiat may be 

 either quite vnde, or very acute, and is sometimes curved, with one 

 edge convex and the other concave. 



To use the lancet, the blade, open at a right angle vrith its 

 handle, is held between the thumb and index finger, while the 



Fig. 174.— Manner of holding a Lancet. 



