. The anatomy of the central nervous system of man and of vertebrates in general. Neuroanatomy; Central Nervous System. THE INTEEBRAIN OE THALAMENCEPHALOlsr. 129 It is known that in the sturgeon a passage leads from the exterior into this preoral gut: , the fundament of a separate mouth is established over the permanent mouth. This whole structure—the preoral cavity and the preoral gut, into which it leads—becomes the hypophysis. According to Kupffer, the evagination from the oral cavity of craniate vertebrates—the hypophysis—is a vestige of this old preoral cavity. In lower vertebrates do
. The anatomy of the central nervous system of man and of vertebrates in general. Neuroanatomy; Central Nervous System. THE INTEEBRAIN OE THALAMENCEPHALOlsr. 129 It is known that in the sturgeon a passage leads from the exterior into this preoral gut: , the fundament of a separate mouth is established over the permanent mouth. This whole structure—the preoral cavity and the preoral gut, into which it leads—becomes the hypophysis. According to Kupffer, the evagination from the oral cavity of craniate vertebrates—the hypophysis—is a vestige of this old preoral cavity. In lower vertebrates dorsal to the infundibulum the posterior wall of the infundibulum is evaginated into a long, narrow epithelial tube whose walls are thrown into numerous folds through the pressure of numerous blood-vessels. The structure is called the Saccus vasculosus (see Figs. 59 and 77). When the posterior end of the ventral wall of the interbrain joins to the base of the midbrain one alwavs finds a farther small evagination:. Fig. 78.—Horizontal section through the hyjiophysis of the ray: Raja clavata. the Becessus mammillaris. In selachia it contains large ridges and nodules of epithelium, and forms a richly vascular structure evidently functional. N"ow that the dorsal and ventral portion of the interbrain have been described, Ave may turn to the consideration of the lateral portions. Close to the epithelial roof there lie the Ganglia hatenulw, one on either side, the distinctive ganglia of the Epitlialamus (Fig. 75). In many of the lower vertebrates there is a difference in the size of the two ganglia; otherwise, however, the Ggl. habenulge offer a good example of a markedly constant brain-structure, varying neither through progression nor retrogression. From Petromyzon to the mammals one always finds them on either side and a little to the front of the epiphyseal process. They consist of two bodies,— a lateral and a median,—and are always separated from the epiphyseal s
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Keywords: ., bookcentury1800, bookdecade1890, booksub, booksubjectneuroanatomy
