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During the oscillographic study of the mode of function of the semicircular canals of the ray (Lowenstein & Sand, 1940a, b), it became clear that the accessibility of the elasmobranch labyrinth and the satisfactory survival of preparations of the labyrinth in the isolated otic capsule opened up the possibility of an extension of the work to the otolith organs in the utriculus, sacculus and lagena. This has now been carried out in experiments described in the present paper. METHODSMale and female rays of a wing span of 15-24 in. were killed by decapitation, pithing, and removal of the brain. The cranium was then isolated and the labyrinth approached through the cartilage at the back of the orbit or from the ventral side. Text- fig. 1 shows a ventro-lateral view of the membranous labyrinth after a maximum exposure of the otolith organs. Openings into the perilymphatic space of a much smaller extent were made for the exposure of individual receptors. In the case of the utriculus the approach was made from the orbit, and nerve twigs from the utricular nerve fan were cut at its proximal end and peeled up towards the lateral margin of the macula. The ampullary nerve branches supplying the anterior vertical and horizontal canals were divided in order to avoid the intrusion of spurious ampullary discharges.In the case of the ramus inferior the posterior ampullary nerve is well out of the way, and the sacculus can thus be isolated by transection of the free-running branch supplying the lagena. The latter is fortunately long enough to allow isolated pure lagena twigs to be peeled off for electrical pick-up. A choice of the region of the sacculus macula to be recorded from was possible owing to the convenient fanning out of the saccular branches of the ramus inferior. Very small twigs could be isolated which, as a rule, contained only a few functional units, the number of which could be further reduced, often to a single functional fibre, by careful crushing of the twig or by its further subdivision by splitting.When the desired twig had been prepared it was picked up in a silver-plated forceps electrode, held in position by a number of rods connected to the preparation holder by rotary clamps. The second electrode was applied to some inner part of the cranium. The holder was then clamped to a tilting device (Text- fig. 2) with the 'nose' pointing in any desired direction. The apparatus was designed for tilting movements about any horizontal axis desired, smoothness of movement and constancy of speed being assured by the use of a 50: 1 reduction gear operated by hand. The wheel at the left was graduated into 360 degrees for the accurate reading of the tilting angle. The slotted

SUMMARY1. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat-with CI and C2 spinal roots cut. Reflex effects were observed as changes in length of the isotonically loaded medial head of triceps.2. The tonic labyrinth reflexes acted asymmetrically on the medial head of triceps. Side-down rotation of the head produced shortening in medial triceps, whereas side-up rotations of the head resulted in a lengthening.3. The tonic neck reflexes acted asymmetrically on the medial head of triceps. Side-down rotations of the neck produced a lengthening of medial triceps, whereas side-up rotations of the neck resulted in shortening.4. Labyrinth and neck reflexes produce opposite effects on the same limb extensor muscle so that, if the neck innervation is intact, head tilting produces no change in muscle length.5. It is suggested that the interaction between the labyrinth and neck reflexes contributes to the stability of the trunk, allowing the head to move freely on the body without affecting this stability. Labyrinth and neck reflexes need therefore to be considered together as a single system.

There is of necessity co-ordination between the activity of the caudal region of the large gut and the behaviour of the sphincters which control the anal canal. There are, however, two sphincters. The internal anal sphincter of smooth muscle receives its motor supply through the hypogastric nerves from the sympathetic outflow and its inhibitory supply through the pelvic nerves from the parasympathetic outflow. The external anal sphincter of striped muscle is controlled by the somatic pudendal nerves. In this case relaxation can only be due to a reduction in frequency of existing motor impulses in the pudendal nerves. Since the two sphincters are superimposed, one upon the other, it is difficult to disentangle the roles played by these two in the control of the anal canal. Garry (1933aGarry ( , 1934 gives diagrams of the anatomical arrangement, with the nerve supply, both in the cat and in man. Floyd & Walls (1953) have an accurate drawing of the actual relationships in man. The nerve supply to the distal portion of the colon and to the anal sphincters of the cat is shown schematically in Fig. 1 of this paper. Garry (1933b) was able to show by mechanical recording in the cat that movement of an object within the distal colon, when the pelvic and pudendal nerves were both intact, led to dilatation of the anal canal. Such dilatation could still be evoked after section of both pudendal nerves had paralysed the external anal sphincter. Thus stimulation of the colon must lead to inhibition of the internal anal sphincter by impulses travelling in the pelvic nerves. But there was no actual proof for inhibition of the external anal sphincter when the colon was stimulated. Such inhibition had to be assumed, otherwise dilatation of the anal canal could not have taken place when the pudendal nerves were intact. This belief that the two sphincters relaxed simultaneously was further supported by the observations of Barrington (1921, 1931) on the reciprocal behaviour of the detrusor muscle of the urinary bladder and the striped