Abstract
The thalamic nuclei of the rat, armadillo, Tupaia, Carnivora, Lemur catta, and Cercopithecus have been identified from cell stained preparations by various authors. These studies are of interest because they form a basis for a comparative study of the thalamus, because a knowledge of the. nuclei is necessary for an accurate study of the connections of the thalamus with other portions of the nervous system, and because a knowledge of both the nuclei and fiber connections is necessary for carrying out and interpreting experimental work on the thalamus. For these three reasons the present investigation has been made.
Five monkey brains were fixed in trichloracetic acid and stained with toluidine blue, according to the technic of Huber. 1 Two were sectioned frontally, 2 transversely, and one sagittally. The cell groupings and arrangements, their separation by fiber masses, and outstanding differences in cell types were used as criteria for designating nuclei.
The nuclei were divided into anterior, middle, midline, lateral, ventral, and posterior groups. The anterior group consists of the anteromedial, anterodorsal, and anteroventral nuclei. They resemble the 3 anterior nuclei of lower mammals, with the exception of the anterodorsal nucleus, which is markedly reduced in size. The reduction of the anterodorsal nucleus is gradual from the lower mammals to the higher.
The nuclei of the medial group are parataenialis medialis and lateralis, medialis dorsalis, medialis ventralis, parafascicularis, centre median, paracentralis, and centralis lateralis. The para-taenial nuclei and the nucleus medialis ventralis are much smaller than they are in the lower mammals, while the nucleus medialis dorsalis and the centre median have increased a great deal. The other nuclei of the medial group are very similar to those of Carni-vora.
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