In decerebrate and decerebellate cats stimulation of any division of the trigeminal nerve induces efferent volleys in the VIIth, Xth, XIth and XIIth nerves. Direct stimulation of the face, internal nares and dura mater produces similar volleys. In uncurarized animals similar stimuli cause twitches of face and neck muscles. Slowing of the heart rate may also be induced. Conduction times measured in the brainstem and cranial nerves show that conduction is very rapid in the brainstem to the level of the obex, so that large medullated fibers may be inferred. At the level of the obex a delay of 2–4 msec. occurs, presumably due to synapses and internuncial neurones. Conduction of the volleys in the Xth and XIth nerves is rapid and large fibers must be involved. Removal of the dorsal vagal nuclei does not abolish the vagal reflex which is presumed to relay at the nucleus ambiguus. The vagal responses are very easily fatigued.

SIXTEEN FIGURERIt has been suggested on anatomical (Green and Harris, '47 ; Green, '51) and physiological grounds (Harris, '48, '55) that a neurohumor secreted in the median eminence of the neurohypophysis regulates the activity of the pars distalis of the pituitary gland. So far the identity of this humoral link has not been established with certainty, one proposal being (Scharrer and Scharrer, '54; Shihusawa et al., '55) that the granular neurosecretory material described by Scharrer and Scharrer ( '40), and Bargmann ( '49) represents this transmitting substance. Thus, neurosecretory material (NSN) from the supraoptic nuclei (SON) and paraventricular nuclei (PVN) or the neurohypophysis is thought to influence adenohypophysial function by way of the supraopticohypophysial tract and the pituitary portal system of blood vessels.This investigation attempts to determine if a correlation exists between the histological aspect of the neurosecretory system and the activity of the pars distalis. The approach adopted was : (1) to submit animals to procedures known to influence the adenohypophysis and then to study the effect on the NSM; (2) to alter the NSM concentration by established methods, investigating the secretory activity of the pars dist a l k Present address: Hofbrouckerlaan 26, Oegstgeest, Holland.

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