Abstract: The effect of morphine, Tinct. opii, loperamide, pethidine and atropine on intestinal transit and the faecal and urinary excretion of water and electrolytes was studied in ponies. The rate of passage of a particulate marker was slowed by morphine, hastened then slowed by loperamide and Tinct. opii, and hastened by atropine. The liquid marker was slowed by Tinct. opii and hastened then slowed by the other drugs. Only loperamide decreased the faecal sodium excretion. This drug also decreased faecal water and weight; it appeared worthy of clinical trial in diarrhoea. Tinct. opii decreased by morphine, pethidine and atropine increased faecal water.

Abstract: In studying behaviour supposedly motivated by fear or by exploration, consideration should be given to the biological functions of these two systems and to the ways in which the experimental environment may affect the performance of ‘natural’ responses. Extreme caution is needed in comparing the effectiveness of different stimuli and the amounts of fear or exploration represented by different responses. In particular, it should never be assumed when making such comparisons that the relative intensities of different stimuli and responses are constant.