VI. Concerning a Possible “Parasympathetic Center” in the Diencephalon

Abstract

In this series of papers it has been shown: (1) that injection of commercial pituitrin into the cerebral ventricles produces a prompt and characteristic reaction presumably stimulating to the parasympathetic; (2) pilocarpine similarly introduced gives a wholly comparable response; (3) an antecedent subcutaneous or intraventricular injection of atropine counteracts the action both of the extract and of the drug; (4) the effector responses do not occur in the presence of lesions which have destroyed or appear to have impaired the functional activity of the interbrain, more particularly its hypothalamotuberal portion, and (5) with patients under the influence of tribromethanol, a narcotic which presumably acts on diencephalic centers, intraventricular pituitrin has either no effect or one which is slight and much delayed. The work of various physiologists, pharmacologists and neurologists is considered in relation to the author''s concept: (1) under emotional stimuli the posterior portion of the pituitary gland becomes discharged through its specific and histologically demonstrable diencephalo-hypophyseal mechanism; (2) the active principle, or a portion of it, enters the cerebrospinal fluid whence, presumably by diffusion through the ependyma, it may act on diencephalic nuclei for the parasympathetic apparatus, and (3) that conditions may arise under which posterior pituitary hormone is discharged into the fluid in amount sufficient to induce a parasympathetic (cranial autonomic) response as diffuse as that of the sympathetic system brought about by epinephrine. The neurohypophysis, in short, may bear a relation to the parasympathetic division similar to that which the suprarenal medulla bears to the sympathetic division of the autonomic nervous system.