SUMMARY1. In anaesthetized cats electrical stimulation of the nucleus fastigius caused cardiovascular responses, electrodermal responses of the paws and pupil dilation with retraction of the nictitating membranes.2. The cardiovascular responses included rise of arterial pressure and peripheral vasoconstriction. Increase ofpulse pressure and tachycardia also occurred.3. The effects of sympathetic blocking drugs indicate that fastigial stimulation causes sympathetic discharge to the heart and to the peripheral vessels. There was no evidence of alteration of vagal activity.4. Fastigial stimulation inhibited reflex bradyeardia due to carotid sinus distension, vagal afferent stimulation or phenyl diguanide.5. Fastigial and hypothalamic influences on cardiovascular responses could be evoked after severing the nervous pathways connecting the two.6. The pressor response to fastigial stimulation was still present after bilateral division of the carotid sinus and vagus nerves.

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6. Such evidence led to the conclusion that there are two pathways for reflex discharge into inferior cardiac and renal nerves, one involving a supraspinal relay and the other confined to the spinal cord.

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EIGHT FIGURESI t has long been known that, when motoneurones have their axons severed, they undergo a prolonged series of histological changes known collectively as chromatolysis. Systematic accounts have been given by Cajal ('09) and more recently by Bielschowsky ( '32) and Bodian and Mellors ('45). There has, however, been singularly little investigation of the physiological reactions of chromatolysed motoneurones. Acheson, Lee and Morison ('42) showed that, following section of the phrenic nerve, there was a deficiency of respiratory discharge along it when compared with the other, control, side. This deficiency ran approximately the time course described for chromatolysis -maximum effect at two to three weeks and recovery several weeks thereafter. Campbell ( '44) found that from 10 days to several weeks after section of a peripheral muscle nerve or of a ventral root there was a complete loss of all monosynaptic reflexes into that nerve or root. On the other hand polysynaptic reflex discharges were even larger than on the control side. He assumed that this polysynaptic reflex was due to cutaneous afferents and that there had been a complete loss of reflex response to impulses in the large proprioceptor fibres of muscle. This assumption was, however, not tested, for all reflex responses were evoked by volleys set up in "mixed" nerves composed of cutaneous and muscle afferents.