The functional organization of the third-nerve nucleus in the cat.

In 1942, Szentagothai showed by means of a modified Horsley-Clarke stereotaxic in­ strument, and a technique of direct stimu­ lation of the oculomotor nerve nucleus that the representation of the striated ocular muscles within this nucleus for the cat and Pose· Com m. Fig. 1 (Danis). Functional organization of the third-nerve nucleus of the cat and the dog according to Szentagothai. the dog is rather different from the one usually admitted. In 1943, Bender and Weinstein repeated this type of experiment on the monkey (Macaca Mulatta). Their conclusions were similar with those of Szentagothai. According to these authors, the distribu­ tion of the radicular cells corresponding to the different eye muscles would be on the following pattern: going from the rostral to the caudal end of the third-nerve nucleus one would have the radicular cells for the inferior rectus, the inferior oblique, the in­ ternal rectus, and the superior rectus. The cells connected with the levator palpebrae would be grouped at the posterior end of the third-nerve nucleus against the fourth-nerve nucleus (fig. 1). Szentagothai was unable to find any func­ tional organization of the nucleus in a dorso-ventral direction. Bender and Wein­ stein believe that the different cell groups have more or less the shape of commas whose tails come under the head of the next anterior group. This arrangement would ex­ plain the fact that stimulation at different depths on the same dorsoventral axis gave different ocular movements. None of these authors was able to show an organization of the nucleus in the trans­ verse plane. This type of experiment does not allow one to determine with certainty whether the innervation of the ocular muscles is crossed, direct, or mixed; it shows, how­ ever, that the majority of cells innervates the ipsilateral muscles. These researches give a scheme of the functional organization of the third-nerve nucleus that is very different from those commonly published in ophthalmic and neu­ rologic textbooks. The scheme more often 1122