. The brain of the tiger salamander, Ambystoma tigrinum. Brain; Ambystoma. 336 THE BRAIN OF THE TIGER SALAMANDER In this specimen the cell bodies are not blackened, and no dendrites are visible. All nuclei of cells are stained, and the gray pattern is clearly shown. There is scanty impregnation of the neuropil. In the cerebral hemispheres only the thickest axons are impregnated; elsewhere the thick and medium fibers are brilliantly differentiated. In some places where the boundaries of fascicles and tracts are obscure, interpretation has been aided by comparison with other specimens by methods
. The brain of the tiger salamander, Ambystoma tigrinum. Brain; Ambystoma. 336 THE BRAIN OF THE TIGER SALAMANDER In this specimen the cell bodies are not blackened, and no dendrites are visible. All nuclei of cells are stained, and the gray pattern is clearly shown. There is scanty impregnation of the neuropil. In the cerebral hemispheres only the thickest axons are impregnated; elsewhere the thick and medium fibers are brilliantly differentiated. In some places where the boundaries of fascicles and tracts are obscure, interpretation has been aided by comparison with other specimens by methods of Cajal, Rogers, Golgi, and Weigert. Horizontal sections are not so favorable for analysis of the tegmental fascicles (chap, xx) as are those cut in transverse and sagittal planes, and it is difficult to follow individual bundles as they recurve around the tuberculum posterius in the peduncle and tegmentum; but, by comparison with sections prepared by other methods and cut in various planes, the courses of most of the tracts and of the tegmental fascicles of groups (1) to (10) can be followed. The limits of the numbered groups of fascicles are not always clear, but their identification by num- ber on the drawings is believed to be substantially correct. tr. op. m. 24 Fig. 25.—Through the ventral part of the anterior commissure ridge and the dorsal border of the chiasma ridge. Only a few of the thicker fibers of the medial forebrain bundle are im- pregnated. These thread their way through the decussating fascicles of the chiasma ridge and spread out in the ventral part of the hypothalamus. The dense neuropil of these regions is not impregnated. All the optic fibers decussate ventrally of this level, except the most dorsal fibers of the axial tract (). The lightly stippled area in the postoptic commissure, marked , contains thin fibers from the dorsal thalamus, which decussate more ventrally (fig. 2C, ). Farther dorsally (fig. 26) these fibers,
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Keywords: ., bo, bookcentury1900, bookcollectionbiodiversity, booksubjectbrain
