Abstract

1. The interaction of acetylcholine and epinephrine has been studied on the small intestine of the mouse, cat, rabbit and dog.

2. Except in the upper part of the cat intestine, acetylcholine produces sustained contractions.

3. These contractions are not appreciably relaxed by epinephrine in the dog, but are in the other three cases. In the cat and the rabbit the relaxation is only transitory.

4. The extent of the relaxation by a given amount of epinephrine is only slightly influenced by varying the amount of acetylcholine used to cause contraction.

5. In the mouse epinephrine is less effective in the upper part as compared to the lower part of the intestine. In the cat and rabbit both parts react similarly to epinephrine.