Intense and very intense reactions were obtained for acid phosphatase, calcium activated ATP-ase (pH 9.4), magnesium activated ATP-ase (pH 7.2) and glucose-6-phosphatase in the cytoplasms of the myenteric plexus nerve cells of the small intestine of Macacus rhesus and rabbit. Nucleotidase activity was moderate or slight and unspecific alkaline phosphatase activity absent. Both ATP-ases presented an intense activity in the myenteric plexus nerve cells of human fetuses 30, 33, and 34 weeks old; 5-nucleotidase activity, slight in the 30-week-old fetuses became more intense in the 33- and 34-week-old fetuses. The satellite neuroglial cells, nerve fibers and blood capillaries presented negative alkaline phosphatase reactions and intense or very intense activities of the other phosphatases.