28 Proceedings of Royal Society of Edinburgh. [sess. 
repeat any of the experiments, it seems wiser to give the details by 
which they and the needless sacrifice of animals thereby entailed 
may be avoided. 
With a careful dissection of the pharynx, the use of an English 
No. 3 catheter without the stilette, a wooden gag with a hole in it 
for the catheter, and notched to receive the upper and lower in- 
cisors, the avoidance of force and the exercise of a little patience, 
the passage of the catheter into the stomach of a guinea pig is 
attended with as little injury as its introduction into the human 
bladder in careful hands. The entrance of the catheter into the 
trachea may be recognised by the character of the breathing, and 
the shorter distance to which it passes without resistance as com- 
pared with the oesophagus. If fluid be injected into the windpipe, 
the animal dies in a few minutes. 
Death occurred several times at first when giving the dose of 
opium tincture recommended by Koch, viz., 1 c.cm. to 200 grammes 
of the animal’s weight, in which cases the animals never awoke from 
the opium sleep. No deaths were caused by giving in repeated 
doses 1 c.cm. or less of the tincture, till the animal was stupefied 
sufficiently to lie on the side or back for ten minutes when placed 
in that position. Several times the dose recommended by Koch 
had to be given, but usually a smaller one sufficed. Of the first 
seven animals dosed with opium alone, by means of a Pravaz 
syringe disinfected with corrosive sublimate solution, and that only 
before the first injection, two animals died on the afternoon of the 
second day, having been lively that morning. These deaths were 
attributed to septicmmia, as no special injury could be detected, and 
none of fourteen animals died that were subsequently injected by 
means of a Koch’s syringe, the needle of which was heated red in 
the Bunsen flame and then allowed to cool before each injection, 
and the glass sterilised in the hot box. Koch’s is more easily steril- 
ised than the Pravaz syringe, there being no piston. 
The animal is held on its back in the left palm, the front abdominal 
walls being projected forwards and made tense on both sides by the 
thumb and fingers, when it is easy to just enter the peritoneal 
cavity w T ith the needle. An assistant should hold the animal’s fore 
and hind quarters. All vessels with which the needle and syringe 
came in contact, as well as all those that contained laudanum and 
