. The American journal of anatomy . Fig. 1 Ventral view of the model of an embryo 2 mm. long (). X pericardium has been removed from in front of the heart. 251 252 FRANKLIN P. MALL I mentioned above in describing the heart of the embryo 2 that its endothelial lining is collapsed and suspended by a massof fine fibrils within the muscular tube. In slightly older stagesthe arrangement of the endothelial lining is changing, becomingdilated on the venous side of the heart. This change is beginningin No. 3, is more advanced in No. 318 and is complete in No. 164(fig. 2). His3 ha
. The American journal of anatomy . Fig. 1 Ventral view of the model of an embryo 2 mm. long (). X pericardium has been removed from in front of the heart. 251 252 FRANKLIN P. MALL I mentioned above in describing the heart of the embryo 2 that its endothelial lining is collapsed and suspended by a massof fine fibrils within the muscular tube. In slightly older stagesthe arrangement of the endothelial lining is changing, becomingdilated on the venous side of the heart. This change is beginningin No. 3, is more advanced in No. 318 and is complete in No. 164(fig. 2). His3 has pointed out that the endothelial lining hugsthe muscle wall closely in the embryonic atrium, while it remainssuspended for a time in the rest of the heart. This arrangementis so pronounced in the early heart that it affords a way by which Fig. 2 From the reconstruction of a heart of an embryo mm. long (No. 164).X 66. View from the left side. we may determine with precision the exact portion of the hearttube from which the atrium arises. My specimens show con-clusively that the atrium arises exclusively from the free hearttube and that the sinus venosus does not contribute to its forma-tion. This being established it follows that as soon as the hearttube is fully separated from the body walls that the anlage of theentire adult heart 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 delica
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
