STIMULATION OF NERVES. 2G1 



introduced into the vessel as already described. A fine pipette 

 must be at hand, made by drawing a piece of glass tubing to a 

 point, and by this the cannula, or cannulce with the attached 

 india-rubber tubing, must be carefully filled with the fluid, so 

 that no air-bubbles remain. The syringe is then connected to 

 it, the slip-knot of the ligature untied, or the bulldogs com- 

 pressing tlie vessel in front of the cannula removed, and the 

 necessary amount injected. The slip-knot is then re-tied, or the 

 bulldogs replaced, if a second dose is to be given. If no more 

 is to be injected, the vessel may be firmly ligatured. 



Division and Irritation of Nerves. — The nerve must be laid 

 bare, and separated from the surrounding connective tissue in 

 the same way as a vessel, especial care being taken never to 

 seize the nerve itself with the forceps. Blood must be removed 

 by a sponge squeezed quite dry, and the nerve must on no 

 account be touched with water. If we wish to remove any 

 adhering clot, or if the nerve happen to get dry through long 

 exposure, it may be moistened with a little saliva or serum. A 

 director is then pushed under the nerve, or we raise it up by a 

 ligature passed below it, so as to secure the adjoining vessels 

 from injury, and we then divide it by a pair of scissors. Very 

 often we wish to have the nerve prepared for section some time 

 before we actually divide it. We then pass the ligature under 

 it and tie tlie two ends together, so as to prevent the ligature 

 from being pulled from below the nerve, and thus form a loose 

 loop by which we can at any moment raise and divide the 

 nerve. 



Nerves may be irritated by pinching, the application of strong 

 saline solutions, or heat ; but more generally we use Pulver- 

 macher's galvanic forceps, which are made of alternate wires of 

 copper and zinc, and dipped in acetic acid, or, still oftener, the 

 interrupted current from Du Bois Kaymond's induction coil. 

 The most convenient electrodes for this purpose consist of two 

 wire points, about a quarter to half an inch long, and an eighth 

 to a quarter of an inch apart. They may either be set in an ivory 

 handle, or they may be simply fixed in a piece of glass tubing 

 by means of cement or sealing-wax, or simply pushed through a 

 piece of cork. 



