. The American journal of anatomy . art is to be found between its arterial and venousattachments. In the embryo mm. long (No. 164) the completed hearttube is seen, which is S-shaped and twisted upon itself so that the 3 His, W., Anatomie mensch. Embryonen. Theil 3, Leipzig, 1885. DEVELOPMENT OF THE HUMAN HEART 253 arterial and venous ends are brought close together. At the venousend the muscle wall is slightly dilated which marks the atrium;this is lined closely with endothelium which encircles the cavitywithin. No delicate fibrils are here seen between the muscle walland its endothelial
. The American journal of anatomy . art is to be found between its arterial and venousattachments. In the embryo mm. long (No. 164) the completed hearttube is seen, which is S-shaped and twisted upon itself so that the 3 His, W., Anatomie mensch. Embryonen. Theil 3, Leipzig, 1885. DEVELOPMENT OF THE HUMAN HEART 253 arterial and venous ends are brought close together. At the venousend the muscle wall is slightly dilated which marks the atrium;this is lined closely with endothelium which encircles the cavitywithin. No delicate fibrils are here seen between the muscle walland its endothelial lining. Then follows an upper bend to theheart after which there is a dilatation projecting towards the leftside, the former marking the atrial canal and the latter the leftventricle. The lower connecting piece unites the left ventriclewith the bulb which later on gives rise to the right ventricle. Inthe atrial canal (Hallers auricular canal) the endothelial tube isseen as a solid strand of cells suspended freely in the muscle wall. Fig. 3 Section of the heart of the embryo mm. long. X 66. by the delicate fibrils already mentioned. In the left ventriclethe tube shows a distinct cavity, while throughout the rest of theheart tube the cavity is irregular but not pronounced. The formof the endothelial tube is shown in fig. 2 and again in a semidia-grammatic figure of a transverse section through the atrium, ven-tricle and bulb in fig. 3. The delicate fibrils, which no doubtbelong to the endothelial cells are present in large number through-out the whole heart tube, excepting in that which forms the another embryo (No. 384, 2 mm. long), considerably smallerthan the one just described and probably pathological, the degreeof development of the heart is practically identical with the one3h mm. long (No. 1(34). 254 FRANKLIN P. MALL In my collection there are two other embryos slightly moreadvanced in development than the one just described which bearupon the exact origin o
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
