Abstract 1. 1. Fresh minced tissue of the brain and spinal cord of Macaca mulatta was found to have appreciable ester-splitting activity. Under standard conditions this activity was approximately the same in different animals of the species. 2. 2. The ester-splitting activity varied throughout the central nervous system. However, tissues obtained from different portions of the central nervous system showed characteristic hydrolyzing activity. 3. 3. The tributyrin-splitting power was greatest in the cerebral cortex, least in white matter, and intermediate in mixed areas. Mixed tissues rich in gray matter, such as thalamus and cerebellum, were more active than mixed tissues rich in white matter, such as stem and spinal cord. 4. 4. The ethyl butyrate-splitting activity was greatest in the cerebral cortex and least in the spinal cord. The cerebellum has less activity than other mixed tissues including the stem. White matter was less active than gray or mixed tissues with the exception of the spinal cord.