. An elementary course of practical zoology. Zoology. ?66 NERVOUS SYSTEM CH. XI seen, in all cases formed from the ectoderm (pp. 202, 209, and Figs. 64, 65, and 143),' and in craniate Vertebrates the anterior end of the hollow medullary tube becomes dilated, forming three bulb-like' swellings—the fore-brain (Fig. 148, A,/ h), mid-brain {m. b), and hind-brain {h. b). Soon a hollow outpushing grows forwards from the first vesicle. jnsd Fig. 147.—Transverse section of embryo of frog. Cixt. ccelome ; cxi', prolongation of coslome into protovertebra (the reference line should end at the space) ; en
. An elementary course of practical zoology. Zoology. ?66 NERVOUS SYSTEM CH. XI seen, in all cases formed from the ectoderm (pp. 202, 209, and Figs. 64, 65, and 143),' and in craniate Vertebrates the anterior end of the hollow medullary tube becomes dilated, forming three bulb-like' swellings—the fore-brain (Fig. 148, A,/ h), mid-brain {m. b), and hind-brain {h. b). Soon a hollow outpushing grows forwards from the first vesicle. jnsd Fig. 147.—Transverse section of embryo of frog. Cixt. ccelome ; cxi', prolongation of coslome into protovertebra (the reference line should end at the space) ; ent. mesenteron (archenteron); jnsd. mesoderm ; nch. notochord ; pr. v. protovertebra ; s£: d. pronephric duct; som. somatic of mesoderm ; sp. c. spinal cord; spl. splanchilic layer of mesoderm ; yk, yolk-cells. (From Parker and Haswell's Zoology^ after Marshall.) (B, prs. en), and the third gives off a similar hollow out- growth (cblni) from its dorsal surface. The brain now con- sists of five divisions: the prosencephalon {prs. en) and diencephalon (dien) derived from the fore-brain, with the pineal apparatus {pn. b, pn. e) and the infundibulum and pituitary body (inf. pty) : the mid-brain or mesen- cephalon (ni. b) which gives rise to the optic lobes and crura cerebri: and the epencephalon or cerebellum (cblm) and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, T. Jeffery (Thomas Jeffery), 1850-1897; Parker, William Newton, joint author. London, Macmillan and Co. , Limited; New York, The Macmillan Company
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