2G0 EXPERIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



muscles are separated from each other by the finger of the 

 operator, or by a blunt aneurism-needle, and any unyielding, 

 connective-tissue may be cut by a pair of scissors. That sur- 

 rounding the vessel itself should be separated from it by the 

 aneurism-needle. A closed pair of forceps may be pushed 

 under the vessel and then opened. This both raises it from its- 

 bed, and lays bare a considerable part of its course. A couple 

 of ligatures are now caught between the jaws of the forceps and 

 drawn through. The proximal end of the exposed part of the 

 vessel is now compressed by a pair of smooth-pointed bull -dog 

 forceps, or a ligature laid in a simple slip-knot ; one ligature is. 

 firmly tied round the distal end, and the second ligature is tied 

 in a loop round the middle, but is not drawn tight. A small 

 piece of calling card, about an eighth of an inch broad, is then 

 slipped under the vessel, so that it may rest on it and remain, 

 steady : its walls are then snipped by a sharp-pointed pair of 

 scissors just on the distal side of the loop. The finder, or 

 aneurism-needle, may be introduced so as to make the opening, 

 more distinct, and, if necessary, this may be enlarged by the 

 points of the forceps being introduced, and then separated. 

 One lip of the divided vessel is seized by the forceps, the 

 cannula introduced, and the loop drawn tight over it so as to tie 

 it firmly into the vessel. The cannula is then tilled by a small 

 glass pipette with the fluid to be injected, the syringe is fitted 

 on, the bull-dog forceps removed, and the requisite amount in- 

 jected. The bulldogs are again put on, and the syringe removed. 

 Injection of Fluids into Vessels. — First, we prepare the solution! 

 to be injected in a test or a watch-glass, and see that the syringe 

 is in working order. The most convenient is one for sub- 

 cutaneous injection, with a glass barrel and a graduated piston. 

 On the piston-rod a small nut screws up and down, so that it 

 can be set to any figure on the rod, and thus prevents it from 

 being any further pushed in, so as to allow the exact amount 

 required to be given at once, but prevent the accidental injec- 

 tion of more than this amount. The end of the barrel must 

 either fit directly into a cannula of the shape shown in Fig. 128> 

 c, or it may be adapted to a glass cannula by tying a small piece 

 of india-rubber tubing to the cannula. The cannula is then 



