Afferent impulses in the oculomotor nerve, from the extrinsic eye muscles

The fact that large numbers of muscle spindles are present in the extrinsic eye muscles of the goat and sheep led us to attempt to record the afferent impulses from these organs in a branch of the oculomotor nerve. It is widely believed that mammalian eye muscles are devoid of muscle spindles, but Cooper & Daniel (1949) reported the finding of upwards of fortyseven muscle spindles in a single human extrinsic eye muscle and comparable numbers in all the other five extra-ocular muscles*. They reviewed some of the literature, both histological and physiological, on the extrinsic eye muscles of mammals, and in the course of comparative studies, they confirmed the finding of Cilimbaris (1910) that muscle spindles are present in the extrinsic eye muscles of the sheep and also the goat. A number of workers have studied the histology of the extrinsic eye muscles of the common laboratory animals but muscle spindles have not been found in them. Cooper & Daniel (1949) confirmed that spindles are not present in the eye muscles of the rabbit, cat, dog and rhesus monkey. However, Sherrington (1897) had demonstrated reflex effects from pulling gently on the inferior oblique muscle of monkeys and cats, and Tozer & Sherrington (1910) showed that many endings of tendon organ type are present in the eye muscles of these animals. These observations have been overlooked by many investigators; de Mare (1928) failed to elicit reflex effects from the eye muscles of rabbits, McCouch & Adler (1932) from those of the cat and Irvine & Ludvigh (1936) from human eye muscles. Corbin & Harrison (1940) state that stretching the eye muscles of the cat gave no sensory potentials in the appropriate nerves, and McIntyre (1941) failed to record afferent impulses in the oculomotor nerves of the cat and monkey. * These findings were demonstrated at the XVIIth International Physiological Congress in Oxford in 1947.