16 EXERCISE IV 



instruments, (1) a bent packing-needle armed with strong string through a 

 hole bored near the needle's point, (2) a cutting bone-forceps ; both are 

 provided. Prepare pericardial manometer and funnel ; also the inductorium, 

 &c., for faradic stimulation of the vagus. 



III. Operation. Some general advice as to operating for physiological 

 work may here be offered. 



Before making the initial incision feel with the finger-tips for bony points which 

 may be indicated, by your instructions or your own knowledge, as helpful guides to 

 the structures you want to expose by your wound. Having determined the direction 

 and extent you mean to give to your skin incision, clip off with coarse scissors the 

 longer hair from the skin, ■ and moisten the skin well with a soaked but squeezed-out 

 pledget from your warm saline. The saline should always be used warmed fully to 



Text-jj-ig. 11. Mode of holding scalpel for a free incision, so as to employ to 

 the full the length of the cutting edge, e. g. when incising skin. 



37" 0. Steadying with the fingers of the left hand the skin above the place where 

 your incision will begin, cut the moistened skin with a quick stroke, employing as much 

 as possible of the whole length of the scalpel's cutting edge. A good method of holding 

 the scalpel for this purpose is ' comme un archet ', like a fiddle-bow (text-fig. 11). The 

 scalpel used should be a fairly large-bladed one, with a freely convex curve of cutting 

 edge — that is, it should not have been worn down to a sort of one-sided dagger, as often 

 are the scalpels brought into the physiology class-room. The same method of scalpel 

 use is effective for any free clean incision wherever required. For physiological work 

 a mode of using the scalpel which should be scrupulously avoided is niggling with the 

 point; slow and ineffective, it causes numerous small haemorrhages, and obscures the 

 deeper structures by leaving frayed edges of fascial and connective tissue. It may be 

 useful in some dissections in the dead animal, but is wholly unsuitable for operating on 

 living tissues. Only in the limited steps of the deeper portion of an operation should 

 the cutting with the knife be confined to the knife's point, and even then but rarely. 



Of course no artery, vein, or nerve desired for experiment should during the operation 

 for its exposure and isolation be for that purpose picked up by the forceps. Such 

 structures should indeed be touched as little as possible, for every touch tends to 

 damage the life of their histological elements. 



