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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![and middle regions suggest the origin of the dorsal aorta from the portion moyenne, any attempt to prove this supposition is met with the difficulty that the aortic cells are known to differentiate.fn situ. To trace a few undifferentiated aortic cells in their migration through mesodermal cells which they closely resemble would scarcely be pos- sible by ordinary embryological methods. In the posterior region the cells adjacent to the medial borders of the lateral plates are not isolated, as in the anterior and middle regions, to form portion moyenne. Fig. 9 shows that the aorta in the posterior region is situate immediately dorsal to the lateral margin of the entodermal pharynx, and, in the posterior part of this region, just dorsal to the medial margin of the lateral plate as well (sections from this part of the posterior region are shown in Figs. 3G and 5G; 7G is slightly anterior to it). The aorta is thus placed exactly in: the line of the mesodermal cells adjacent to the medial borders of the lateral plates apparently arises directly from them. In the foregoing notes an attempt has been made to bring together some evidence bearing on the development of the vascular endothelium of the head in order to arrive at a conce])tion of the nature and rela- tions of the endocardium. The evidence in question appears to justify the statement that the endocardium in shad arises from meso- dermal cells which are found, after differentiation of tlie lateral plates, to be placed in the region bordering on the medial margins of the latter; further, that the mesodermal cells in this situation appear to be given up exclusively to the formation of vascular endo- thelial cells of which tlie endocardium only forms a part. A few words may be added by way of re-examination of the “Portion moyenne du mesoblaste” of Swaen and Brachet. In the anterior pericardial region the cells which later form the endocardium must necessarily be separated from the somital portion of the meso- derm, for the former eventually take their place as endocardium ventral to the lateral plates, while the latter retains its position dorsal to them. In the middle and posterior pericardial regions, separation of the cells bordering on the lateral plates is not a neces- sity, for neither region produces endocardium. Nevertheless, separa- tion occurs in the middle region but not in the posterior; the dif-](https://iiif.wellcomecollection.org/image/b22426085_0038.jp2/full/800%2C/0/default.jpg)
