. The anatomy of the central nervous system of man and of vertebrates in general. Neuroanatomy; Central Nervous System. 166 ANATOMY OF THE CENTEAL NEEYOUS SYSTEM. of the septum^, divides the whole inner side into a dorsal and a ventral por- tion. Only the dorsal portion is covered with cortical tissue. This sulcus, which thus forms the ventral boundary of the brain-cortex, persists through- out the whole animal series after its appearance in the reptiles. In the accompanying figure (114) it is called Fissura arcuata septi, but in mammals it is called the "inner marginal ;' In
. The anatomy of the central nervous system of man and of vertebrates in general. Neuroanatomy; Central Nervous System. 166 ANATOMY OF THE CENTEAL NEEYOUS SYSTEM. of the septum^, divides the whole inner side into a dorsal and a ventral por- tion. Only the dorsal portion is covered with cortical tissue. This sulcus, which thus forms the ventral boundary of the brain-cortex, persists through- out the whole animal series after its appearance in the reptiles. In the accompanying figure (114) it is called Fissura arcuata septi, but in mammals it is called the "inner marginal ;' Into the cortex which covers the dorsal portion of the septum an im- portant bundle regularly enters: the T7\ olfactorius septi. It arises from the olfactory apparatus of the base of the brain; its fibers converge toward the median brain-surface, thence pass upward and backward into the cortex. The region in which it ends is, on this account, called the olfactory cortex. In amphibia, with uncertainty, demonstrable; this bundle is always promi- ^et«"^. Fig. 115.—Sagittal section through the brain of a chicken. nent in reptilia and mammalia (see Fig. 114). In birds, however, it is veiled by a bundle, which is especially developed in these animals—Tr. septo- mesencepJialicus-—and which, arising in a wide origin from the dorsal portion of the cortex near its edge where it turns outward, is spread out upon the inner surface of the avian brain like a broad, white fan. Eeaching the base of the brain, it encircles it with externally directed fibers, and just anterior to the optic tract, which it reaches on the lateral aspect of the brain, passes again upward and backward to disappear in the most anterior portion of the roof of the midbrain. Thus this tract connects the midbrain with a par- ticular cortical region (Fig. 115). It is foreshadowed in reptiles, but has not been located in mammals. If one makes a frontal section through the forebrain of any of the. Please note that
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