A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . nged themselves in a single layer surrounding thelumen of the heart. In the triton embryo, according to Mollier (1906),at the time when the heart is in its earliest stages,isolated angioblast cells appear between endodermand mesoderm at various places along the sides oftlie embryo, but especially near the boundary betweenthe lateral and the ventral mesoderm. The ventral band of angioblast is the so-calledblood island. The cells in the periplieral portionof this ban
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . nged themselves in a single layer surrounding thelumen of the heart. In the triton embryo, according to Mollier (1906),at the time when the heart is in its earliest stages,isolated angioblast cells appear between endodermand mesoderm at various places along the sides oftlie embryo, but especially near the boundary betweenthe lateral and the ventral mesoderm. The ventral band of angioblast is the so-calledblood island. The cells in the periplieral portionof this band develop into an endothelial tube, thesubintestinal vein, while the cells that are enclosed 2i: Eiood-Tasoular System,Origin of REFERENCE HANDBOOK OF THE MEDICAL SCIENCES in this vessel become blood corpuscles. This is thesole source of blood in the joung embryo. All the restof the angioblast gives rise to empty vessels which,by anastomosis, become connected with the subin-testinal vein and receive their blood from it. Ac-cording to MoUier the angioblast cells that form theaorta and cardinal veins arise in silu on the inner. Fig. 818.—Frontal Section of a Triton Embryo with Nine-teen Segments, ag. Anterior branch of ventral band of angio-blast; am, mandibular artery; h, heart; I, liver; m, mesoderm;pc, pericardium; p/i, pharynx; p, omphalomesenttiric vein. (AfterMoUier.) surface of the mesoderm, and have not wandered infrom the ventral side. In the amphibia and other vertebrates that haveholoblastic eggs, the whole o\aim develops into theembryo, and in these the development of the blood-vascular system is of the primitive type that has justbeen described. In contrast with this, we have thetype found in the animals with meroblastic eggs(see Segmentation of the Ovum), including themajority of the fishes, the reptiles, and the birds,and also the mammals which, although having usuallyholoblastic eggs, follow the Sauropsidian type ofdevelopment. In these animals, the blastoderm(q
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Keywords: ., bookauthorbuckalbe, bookcentury1900, bookdecade1910, bookyear1913
