Following section of the sympathetic trunk in the pigeon and fowl the wing does not maintain its characteristic flexed and adducted position while at rest. Following section of the dorsal roots of the brachial plexus, leaving the sympathetic trunk intact, the muscles of the wing are not atonic, but tend to maintain the wing in any position in which it is passively placed. Following section both of the dorsal roots of the brachial plexus and the sympathetic trunk the muscles no longer exhibit the tendency to maintain the wing in any given position. These experiments are essentially a repetition, with corroborative results, of certain of Hunter''s experiments on birds. Removing the sympathetic nerve supply to the muscles of a limb in dogs usually produces no effect discernible by palpition or by direct observation during the normal behavior of the animal. However, when such animals are anesthetized, these muscles are more flaccid than those of the other limbs. Spiegel''s method was used in tonus measurements on the quadriceps femoris muscles. The results obtained before and after unilateral extirpation of the lumbar sympathetic trunk show that the tonus is materially reduced. Removal of the cerebellum results in reduction in tonus if the sympathetic innervation is intact; but not otherwise.