Quain's elements of anatomy . milarto that of the vessels, in so far that it is by the vacuolated formation of oneor of two main tubular spaces within groups of mesoblastic cells that thecavity of the organ originates (see fig. 744, p. 838). But the formation Fig. —Outlines op the anterior HALF OP THE EJIliRYO CHICK VIEWEDFK03I BELOW, SHOWING THE HEART INITS KAKLIER STAGES OF F0R3IATI0N. (After Hemak.) =f A, embryo of about 28 to 30 hours ;B, of about 36 to 40 Lours ; a, anteriorcerebral vesicle ; h, proto-vertebral seg-ments; r, cephalic fold ; 1, ], vitellineor omphalo-mesenteric veins
Quain's elements of anatomy . milarto that of the vessels, in so far that it is by the vacuolated formation of oneor of two main tubular spaces within groups of mesoblastic cells that thecavity of the organ originates (see fig. 744, p. 838). But the formation Fig. —Outlines op the anterior HALF OP THE EJIliRYO CHICK VIEWEDFK03I BELOW, SHOWING THE HEART INITS KAKLIER STAGES OF F0R3IATI0N. (After Hemak.) =f A, embryo of about 28 to 30 hours ;B, of about 36 to 40 Lours ; a, anteriorcerebral vesicle ; h, proto-vertebral seg-ments; r, cephalic fold ; 1, ], vitellineor omphalo-mesenteric veins entering theheart posteriorly ; 2, tlieir union in theauricle of the heart; 3, the middle partof the tube corresponding to the ventri-cle ; 4 (in B) the arterial bulb. of the walls of the primitive heart is due, not merely to the accumulation and differentiation of the mesoblastic cells in the region which it at first occupies, but is also effected by a folding of mesoblastic layers round the cavity. In these folds two sets. theof G5S THE BLOOD-VASCULAR SYSTELl. cells are distinguishable from a yeiy early period, viz., 1, those ofa more delicate character and looser disposition in which the spaceor spaces for the hearts cavity are more immediately formed, andwhich afterwards range themselves ronnd that cavity in the form ofan endocardiac lining, and, 2, those forming a thicker layer whichimdergoes inflection, and which give rise to the muscular part of Fig. 763
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Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy
