1. Piglets were left to suckle their dam for about 2 days after birth to obtain colostrum and were then divided into four groups. One group was left with the sow, the second was given a standard liquid diet based on cow's milk, the third the standard diet with lactic acid added to give a pH of 4.8, and the fourth the standard diet with the casein content increased by 50%. Stomach samples were removed at intervals by stomach tube for pH measurements and bacteriological investigations. The tube was used immediately to give barium sulphate for radiographic examinations and was then withdrawn. Comparisons were made between treatments and between scouring and non-scouring piglets.

2. A diarrhoeic (scour) syndrome frequently developed; this was always preceded by diminishing gastric activity leading to gastric stasis. When spontaneous recovery occurred, there was a return of gastric function before recovery from scours and before the resumption of normal weight gain.

3. The incidence, duration and severity of the scour syndrome was less in piglets left on the sow; these differences could not be ascribed to the effect of colostrum. Piglets receiving the lactic acid milk diet had an average gastric pH of 1 unit less than the other piglets. Although the severity of scour and loss of clinical condition was less in the piglets given lactic acid milk the duration of reduced stomach motility was the same as in the other artificially fed piglets.

4. No obvious correlation was shown between the scour syndrome and the bacterial flora of the stomach or the intestines. The gastro-intestinal tracts of the piglets given lactic acid milk contained fewer bacteria than those of the piglets on the other diets.

5. Gross between-treatment differences at post-mortem were evident only in the stomach.

6. The spontaneous scour syndrome observed under the conditions of these experiments appeared not to be of bacterial origin but to be associated with a physiological malfunction of the stomach.