INSTRUMENTS. 255 



divided into compartments, one for each kind of instrument. 

 It is advisable, also, to have an extra instrument or two of each 

 sort. 



Wai/ of Making Cannulce. — Cannulae for injecting into vessels 

 may be made of metal (Fig. 128c) or of glass. Glass ones can 

 be easily made of any size required by heating a piece of glass- 



FiG. 128. 



A is a metal cannula with an ear e, by -wliich it can be fastened to any tube 

 connected with its large end. B is an instrumeut for introducing A into a 

 vessel. It consists of a piece of metal tubing, with a jiointed piece of wood at 

 one end, over which A is put. The point projects through the small opening 

 in A, so as to enter the lumen of the vessel readily, c is a metal cannula 

 which fits on the end of a sjricge for injecting fluids into vessels, d is a glass 

 cannula. The dotted line shows the original tube drawn out in the blow-pipe 

 flame ; the darker line shows the finished cannula, e and f are two pieces of 

 glass tubing drawn out to make pens. They may be attached bv pieces of cork 

 to any writing apparatus. Gh is an aneurism-needle. 



tubing over the flame of a blow-pipe, and drawing it out in the 

 middle, as represented by the dotted line (Fig. 128d). It is then 

 heated at a and slightly drawn out, so that a bulging piece is 

 left between a and c ; it may then be heated and very slightly 

 drawn out at &, then cut with a three-cornered file at c, and the 

 point ground obliquely off on a hone. If the point be at all 

 sharp, its edges may be rounded in a gas-flame. When the 

 cannula is introduced into a vessel, a ligature at a prevents it 

 from coming out : it may be connected with a syringe or with 

 any piece of apparatus by a piece of india-rubber slipped over 



