. Contributions to embryology. Embryology. -Section through the cyclopean eye of erabrjo No. 201. 1'', first branch of fifth nerve; S, snout. isolated braiii-inays between the eye and the large mass just described. By com- paring these structures with a i)rofile reconstruction of the forebrain of the cyclo- pean embryo No. 559 (plate 1, fig. 1), the larger mass just above the ganglion of the fifth undoubtedlj'^ represents the interbrain, as the free end of the optic nerve reaches just to its base but does not enter it. The crescent- shaped mass of the brain in front of the interbrain is the un
. Contributions to embryology. Embryology. -Section through the cyclopean eye of erabrjo No. 201. 1'', first branch of fifth nerve; S, snout. isolated braiii-inays between the eye and the large mass just described. By com- paring these structures with a i)rofile reconstruction of the forebrain of the cyclo- pean embryo No. 559 (plate 1, fig. 1), the larger mass just above the ganglion of the fifth undoubtedlj'^ represents the interbrain, as the free end of the optic nerve reaches just to its base but does not enter it. The crescent- shaped mass of the brain in front of the interbrain is the unpaired single cerebral vesicle, which communicates freely with the ventricle of the interbrain. The structure of the wall of this degenerated cerebral vesicle cor- resjjonds very closely with that of the small vesicle in embryo No. 559. With these structures established, as shown in the ])rofile reconstruction, it is pos- sible to identif}' some of the re- maining structures of the orbit. However, the tissues are very greatly dissociated, and for the present it is impossible for me to follow them farther than is given in the following description. First of all, the three branches of the fifth nerve can be fol- lowed to their termination. The first branch reaches up to the rudimentary snout, where it anastomoses with its fellow from the opposite side—shown also in the dia- gram (fig. 3). This snout, by the way, is represented l)y a slight elevation in the middle of the face above the eye, and sections through it show that it is composed of a relatively large, irregular of cells which are .sepa- rated more or less from tlie surrounding mesenchyme. Within the middle of this mass is a small pearl-like l)ody about mm. in diameter. Just behind this body the first branch of the fifth nerve anastomoses across the midline. The second branch of the fifth runs below the eye on either side and reaches nearly to the skin, where it spreads out into several large branches. The thi
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Keywords: ., bookauthorcarn, bookpublisherwashingtondc, booksubjectembryology
