Hydrogen-ion concentration in the gastro-intestinal tract of the albino rat.

Abstract

In order more accurately to interpret various findings in nutritional studies with albino rats, it was desired to ascertain the normal alimentary conditions of the rat, with special reference to the hydrogen-ion concentration.

Adult male rats were fed various diets, for periods of from one to nine days, except when otherwise noted below. The food was given ad lib., and the rats were killed several hours after the last day's supply of food had been placed in the cage. The contents of the stomach were promptly removed and filtered through glass wool. The small intestines were divided into two portions of equal length, and the contents gently expressed and filtered. (The scant volume of the intestinal contents made it impracticable to make definite comparisons of the various anatomical divisions of the intestines.) The pH of each fluid was then determined colorimetrically, using the Clark and Lubs indicators, and using standard phosphate solutions which had been checked electrometrically. When necessary, a comparator was used in matching colors.

The diets used were: our standard mixed diet (which includes meat, milk, cheese, corn, rye, oats, bread, cabbage); lean beef alone; beef fat alone; boiled potato alone; Pappenheimer and Sherman's rachitic diet “84” (flour 95 per cent, calcium lactate 2.9 per cent, sodium chloride 2 per cent, ferric citrate 0.1 per cent); and the Pappenheimer-Sherman diet plus five per cent cod liver oil.

In the rats on the mixed diet, and on lean beef, fat, and potato diets, we found varying degrees of acidity throughout the tract, as summarized in the tables below.

In the experiments on the Pappenheimer-Sherman rachitic diet, eight rats were used. After seven weeks on this diet, four of the rats were killed and their gastric and intestinal contents studied.