[Comparative morphology.]

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1879 Excerpt: ...inner olfactory tracts arise near the anterior commissure, cross each other, and pass into the olfactory lobes. (3) In the Reptiles Chelonia), the cerebral commissures lie below and slightly in front of the foramina of Monro. The larger upper bundle ascends in front of the foramen and divides. The anterior division, or corpus callosum supplies the whole of the inner mantle. The small posterior division supplies the inner fold of the hemispheres and represents a portion of the fornix. The lower bundle is the anterior commissure. It consists of an upper tract the pars olfactoria, the distribution of which is doubtful; and of a lower tract the pars temporalis which is distributed as in the mammalia. In connection with the corpus callosum is a bundle representing a portion of the fornix. (4) The position of the cerebral commissures in the Birds (Columba) is similar to that in the Reptiles: The upper bundle is very small. It divides and is distributed as in the Reptiles but the division representing the corpus callosum is much smaller than that representing the fornix. The anterior commissure consists principally of the pars temporalis, the pars olfactoria being reduced or wanting. The corpus callosum is larger than the anterior commissure in the Amphibia and Chelonia but in birds it is much smaller. These proportions are in relation to the thickness of the inner mantle. In the birds accordingly, where the inner mantle has suffered the greatest reduction, the corpus callosum is a mere rudiment. In the other groups described it is far from rudimentary. In comparison with what we observe even in the lowest mammals, the size of the cerebral commissures is diminutive in proportion to that of the hemispheres (cf. figs. 1 and 2 al. With the distribution, text area in ...