CHOLINE ACETYLASE IN MAMMALIAN AND AVIAN SENSORY SYSTEMS

1. The activity of choline acetylase in tissues of birds and mammals has been measured by a method which excludes possible errors due to variations in the rate of CoA acetylation. 2. By this method it has been found that the optic nerves of mammals and the chicken contain little or no choline acetylase; and the sensory roots of bullocks also contain no enzyme. 3. The chicken retina can produce more acetylcholine per unit weight of tissue in a given time than any other vertebrate tissue yet examined. The pigeon retina is also exceptionally active; and in both species the optic lobes also contain high concentration of enzyme. 4. The distribution of choline acetylase in the optic system of all species examined supports the idea that in this system cholinergic alternate with non-cholinergic neurones.