The intestines of the rabbit are apparently much more sensitive to the action of sodium citrate and sulphate than are those of the dog or cat. Barium chloride, on the contrary, acts with equal strength in all these animals. In a rabbit, the intestines are always set in active peristaltic movement by contact with m/8 sodium citrate solution; and even much more dilute solutions are, as a rule, effective. In a cat, however, it was found that an m/8 solution of sodium citrate has practically no effect, while a ⁵⁄₈m solution sets the intestine in active motion. In a dog also m/8 sodium citrate solution is usually ineffective. Similarly an m/8 sodium sulphate solution is inactive in a dog while an m/2 solution of the same salt starts up distinct peristalsis. In the cat and dog also the peristalsis may be inhibited by calcium or magnesium chloride, as shown in the following experiments. The intestines of a cat were exposed in the usual manner, and an m/8 solution of sodium citrate was applied to the serous surface of the loops. There was no increased movement. There were then poured on the loops a few cubic centimetres of a mixture of 5 c.c. ⁵⁄₈m sodium citrate and 5 c.c. ⁵⁄₈m CaCl_{2}. The loops remained motionless. After waiting a considerable time (15 minutes), a ⁵⁄₈m solution of sodium citrate alone was poured on the intestine. Almost immediately they became very active; and the peristalsis continued until calcium chloride was again applied. The loops then came to a standstill. The difference in susceptibility to the action of citrate which exists between rabbits on the one hand, and dogs and cats on the other, may be in some way connected with their being herbivorous and carnivorous animals respectively.