An attempt to locate cells of kinaesthetic sensibility in extraocular eye muscles.

Abstract

Experimental work on dogs, cats, and pigs has thus far yielded the following positive findings. The cells of the III, IV, and VI cranial nuclei of the dog and cat can be separated into two distinct sizes, hitherto unrecognized, both having “motor” tigroid substance, and being in general diffusely intermingled throughout the nuclei. The smaller cells do not preponderate in any portion of the III, IV, or VI nuclei, nor in any of the subnuclei of the III, except Perlia's median nucleus which, in the dog, is made up entirely of the smaller cells. In the dog, the proportion of the sizes of the cells by actual count correlates roughly with the sizes of fibers in the peripheral trunks, more especially in the case of the third cranial pair. There is in the dog an excess of cells in the central nuclei of the extraocular muscles over the number of fibers in the peripheral homologous trunks, roughly, 30 to 40 per cent for the Nn. III and IV, and 10 per cent for the N. VI. Adequate clumps of cells along the peripheral nerves for the mediation of kinaesthetic sense of the extraocular muscles have not been demonstrated. The accumulated evidence of experiments with degenerations thus far indicates the possibility that the smaller cells in the central nuclei may mediate kinaesthetic sense of the extraocular muscles. The problem is being attacked further.