DISSECTIONS. 



139 



examine the contents of natm-al ca\ities, or to pro%ide for the escape 

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

 small 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 bistoury, the 

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

 bistomy, with a poiated and two-edged blade. The point may be 

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

 edge convex and the other concave. 



To use the lancet, the bladfe, open at a right angle wdth its 

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



Fig. 174.— Manner of holding a Lancet. 



