Influence of continued administration of morphine and of withdrawal on contraction of small intestines of dogs.

Two experiments were carried out on dogs with Thiry-Vella fistulae of ileum. The operations for formation of the fistulae were performed several weeks before the experiments were started. Graphic records of the intestinal contractions were made by introducing into the fistula a sausage-shaped rubber balloon fastened on a catheter and filled with water; the catheter was connected with a Brodie bellows-recorder which made the tracing on a slowly moving kymograph. Records were made in this way without anesthesia or operative procedure or discomfort to the animal.

Experiment 1. Ascending doses of morphine sulphate: A female collie dog, weighing 21 kg. received daily hypodermic injections for 71 days and during this time the dose was increased from 1 mg. per kg. to 25 mg. per kg. There was some constipation and loss of appetite but the dog remained in good condition, losing only one kg. in weight. Narcosis and vomiting disappeared after the fourth week, but salivation continued throughout the experiment. The dog became shy and restless as the experiment progressed.

Graphic records of the effect of the injections of morphine on the intestinal contractions were made at intervals of two to three days throughout the experiment. There was no change in the character of the reaction at any time. We have reported in a recent paper 1 that hypodermic injections of morphine in dogs greatly increase the muscular activity of the intestine. In this experiment each injection produced the usual reaction; marked increase in tone and in amplitude and frequency of the contractions. From time to time small doses (0.15 mg. per kg.) were injected before the regular daily dose, and these invariably produced stimulation of the intestinal contractions.