Abstract
The following method of studying peristaltic movements of the intestines in situ has been found extremely useful by the writers in connection with an investigation of certain purgatives and is deemed worthy of description for the benefit of other investigators because it is simple, efficient and economical.
A white rat, previously starved for 24 hours, is anesthetized with an intraperitoneal injection of urethane. This anesthetic has been found by the writers to act with extraordinary rapidity in the rat, so that an injection of 1.25 gm. (using a 4% solution) per kilo weight of rat produces complete and deep anesthesia within 5 minutes, lasting for 5 or more hours without any appreciable depressant effect on the heart or respiration. Doses of 1.5 gm. per kilo produce an anesthesia lasting for 24 hours or more, while 1.0 gm. per kilo produces an anesthesia of shorter duration. The rat is tied on a small dissecting board and immersed in physiological saline solution at body temperature, care being taken to keep the head out of. the water. A median incision is made through the abdominal wall, without producing any bleeding, and the intestines are allowed to float on the saline solution. For the study of the intestinal movements and the passage of food through the gastro-intestinal canal, a small quantity of India ink (0.5 of 1.0 cc.) is introduced directly into the stomach by injection through a fine catheter passed through the mouth and oesophagus into the stomach. The passage of food and gastric contents through the intestinal tract of the rat is a very rapid one, the whole length of the intestine being traversed ordinarily in an hour's time. This passage, or movement, of the intestinal contents mixed with the India ink or finely divided carbon particles can be plainly followed with the naked eye because the thin intestinal walls of the rat allow the dark contents to be seen through them.
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