. The anatomical record. Anatomy; Anatomy. The Anatomical Eecord. 421 Fiff. 3 shows a reconstruction of these vessels and their relation to the myotomes. I regret that we can not speak more definitely of their relation to the dorsal, so-called "segmental" vessels, not that their posi- tion could thus be determined any more positively than it already has been by reference to the myotomes, but for quite another reason. In the Birds, where we now have the most complete account of the earliest limb vessels, the subclavian arteries are primitively independent lateral offshoots of the aort
. The anatomical record. Anatomy; Anatomy. The Anatomical Eecord. 421 Fiff. 3 shows a reconstruction of these vessels and their relation to the myotomes. I regret that we can not speak more definitely of their relation to the dorsal, so-called "segmental" vessels, not that their posi- tion could thus be determined any more positively than it already has been by reference to the myotomes, but for quite another reason. In the Birds, where we now have the most complete account of the earliest limb vessels, the subclavian arteries are primitively independent lateral offshoots of the aorta and only later come to be included as branches of the dorsal segmentals. It is not unlikely that our case represents this primary condition in Man. In Chiller's embryo, which is slightly older,. Fig. 3. Reconstruction of position and course of segmental subclavian arteries present in this case. 7tli seventh cervical intersegmental space; 1st , first thoracic intersegmental space. the subclavians are already definitely branches of the corresponding dorsal vessels. Eelation of the Foregoing to the General Principles of the Development of the Vascular System. It has already been emphasized that the dispute on the method of development of the subclavian has established clearly the two modern views on the development of the vascular system. According to the one, blood vessels grow out to their territory as definite stems from the very beginning; whereas, according to the other view, they are always preceded by a capillary plexus the conversion of which into the later stem or trunk involves the selection of one path through the mesh and the atrophy of all or most of the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bardeen, Charles Russell, 1871-1935, ed; Boyden, Edward A. (Edward Allen), 18
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