Quain's elements of anatomy . Fig. 76S.—Transverse section through the head op an embryo rabbit of eioht DAYS AND FOURTEEN- HOURS, WITH A PART OF THE PERIPHERAL BLASTODERM. \*. (From Kolliker.) hh, rudiments of the heart; sr, pharyngeal groove. where it receives the inflection of the mesoblastic cells, Avhieh form itsmuscular wall. But in others, such as mammals, in which the fact wasfirst discovered by Henscn Qso. 88), in osseous fishes, and to some extentalso in birds, in wliich the enclosure of the pharyngeal cavity by the in-flection of the cephalic fold is of later occurrence, the heart h
Quain's elements of anatomy . Fig. 76S.—Transverse section through the head op an embryo rabbit of eioht DAYS AND FOURTEEN- HOURS, WITH A PART OF THE PERIPHERAL BLASTODERM. \*. (From Kolliker.) hh, rudiments of the heart; sr, pharyngeal groove. where it receives the inflection of the mesoblastic cells, Avhieh form itsmuscular wall. But in others, such as mammals, in which the fact wasfirst discovered by Henscn Qso. 88), in osseous fishes, and to some extentalso in birds, in wliich the enclosure of the pharyngeal cavity by the in-flection of the cephalic fold is of later occurrence, the heart has at first theremarkable form of two tubes separated to some distance from each ofchei,and the formation of the single and median cavity of the heart isdue to the gradual apjjroxiniation of these tubes aud their coalescence-Fig. 769. mcs fi-. 769.—Part of the foregoing figure more highly magnified. ?-.(From KolJiker.) rf, medullary groove ; riv, dorsal ridge ; mf, medullary plate and rudiment of thebrain; /(, epiblast ; lip, j^arietal wall ; dfp, visceral mesoblast, inflected into theouter wall of the heart akli ; ihli, inner or endovascular lining of the heart; ph, ijericardialcavity ; i^us, mesoblast beyond the rudiments of the heai-t; dd, hypoblast ; (W, noto-chord ; sw, lateral wall of the developing x^harynx. into one by the union and subsequent disappearance of the adjacentparts ,of their primitive walls. In the case of the heart being thus atfirst double, each tube receives posteriorly the large entering vein, and isprolonged anteriorly into the issuing vessel or artery ; while in themedian single heart, whether formed originally so, or by later fusion oftwo tubes, the posterior part receives the two entering veins, wliile theanterior part opens into the two primitive outgoing arteries. sso TEE BLOOD-VASCULAll SYS
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Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy
