The development of the heart in shad (Alosa sapadissima, Wilson) : with a note on the classification of teleostean embryos from a morphological standpoint / by H.D. Senior.
- Senior, H.D.
- Date:
- 1909
Licence: In copyright
Credit: The development of the heart in shad (Alosa sapadissima, Wilson) : with a note on the classification of teleostean embryos from a morphological standpoint / by H.D. Senior. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![which, it api)cars from the literature, have previously escaped notice. Firstly: The endocardial cells do not descend in a hap-hazard fashion; descent proceeds, in a perfectly orderly manner, continu- ously from before backwards; the last cells to descend (i. e., those in the region of the future aorta) are arrested, as it were, in the act of descent to form the first part of the central aorta. Secondly: In the region posterior to the aortic root descent of endocardial cells does not occur at all; the endocardium in this region is exclusively fur- nished by cells descending in, and derived from, the region anterior to the root of the aorta. The part of the portion moyenno, which at 15 somites was easily recognizable in the region behind the (future) aortic root, extending back as far as the middle of the otocyst( see Figs. 3E and 3F), has disappeared long before the completion of the heart anlage, apparently by blending with the adjacent somital mesoderm. It is still recog- nizable at 18 somites (see right side of Fig. 4E), but posterior to this it has already disappeared or is very indefinite, see left side of Fig. 4E (through their hyo-branchial anlage). At 22 somites the portion moyenne, in this region, has entirely disappeared. Review of the evidence heaHiig on the relation of the endocardium to the vascular endothelium of the head m general. The development of the pericardial coelom, including in this term the future myo-epicardium, may be looked upon as a subject prac- tically complete in itself which can be considered independently of that of other structures. The case of the endocardium is entirely different; the fact alone that part (at least) of the ventral aorta arises, in common with the endocardium, from the portion moyennne is quite sufficient to indicate that the endocardium cannot be con- sidered as an inde]K‘ndent structure. It is only reasonable to sup- pose that the origin of the aorta is essentially similar throughout tlie head, so that separation of the aorta from the endocardium, in this connection, would be artificial and, therefore, not conductive to a clear conception of the origin and relations of the latter. During the study of the process of formation of the heart anlage several facts bearing on the origin of the vascular endothelium became](https://iiif.wellcomecollection.org/image/b22426085_0034.jp2/full/800%2C/0/default.jpg)
