Sixteen animals weighing from 450 to 900 gm. were studied by Dr. Helene King over periods varying from 13 to 66 days. The guinea-pig is so foreshortened that the gastrostomy operation was beset with some difficulties-the fundic portion of the stomach is pushed up under the diaphragm in such a manner that it must be pulled downward and stitched to the abdominal wall to make a fistula, or an opening must be in the pyloric region. Both methods proved satisfactory, and the possible objection to the lower opening that the balloon did not lie in the fundus was obviated by the use of a small balloon or of a finger cot from 3 to 5 c.c. in capacity, pushed well up into the stomach. Several animals killed with the balloon in place left no doubt of the ease with which it was properly inserted. Very small fistulas were made so that when the wounds healed they often measured less than 1 cm. across. Since the animals began eating within 12 hours, the food in the distended stomach prevented the openings from closing.
The guinea-pig, like other herbivorous animals, feeds at frequent intervals-probably every hour-and under normal conditions the stomach is never found empty. Even within 2 .hours after exclusion from food it begins eating its own excreta, a fact noted by other observers, and after 12 hours will eat paper, pasteboard, or anything of that nature within reach. The easiest and most effective method found for excluding it from its own feces was to place the body of the animal in a bag, sufficiently small to prevent much freedom of movement, and then to draw the bag closely about the neck.
In the guinea-pig contractions of the stomach were observed in 5 hours after taking the food away. Frequently continuous records were made from the time the food was removed until the onset of such vigorous movements. The mild peristaltic waves of digestion become more and more intense until contractions such as might be classified as type I appear-that is, periods of tonus lasting 2 or 3 minutes with 4 or 5 superimposed contractions. This type may continue for 4 hours, but they gradually merge into the more vigorous type II and possible type III. The contractions follow one another in rapid succession-one in 18 seconds on the average- such a period terminating in complete quiescence of the stomach. At times a period of violent coughing precedes the inhibition. Contractions of types I and II have been recorded continuously for 6 hours with but two periods of rest lasting 8 and 6 minutes respectively.
That discomfort is experienced by the guinea-pig when food is withheld for even 4 or 5 hours is evidenced by restlessness, the eating of the animal's own excreta, chewing movements, and sometimes crying, when the contractions are unusually vigorous. The animal evidently experiences hunger while the stomach still contains an abundance of food.