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
Catalogue details

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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    In the formation of the heart-tube anterior to the aortic region, the splanchnic mesodenn of the right side undergoes active movement, while that of the left remains comparatively passive. The splanchnic mesoderm to the right of the heart-tube axis arises abruptly from the somatic layer to form a crest which moves over to the left; this ' crest becomes imminent and falls to the left somewhat in the manner of a wave breaking upon the shore (see Fig. IIC). The splanchnic mesoderm to the left of the axis rises slightly to meet the splanchnic mesoderm from the other side as the latter falls; between the two a tube of splanchnic mesoderm is formed of which the ventral wall is derived mainly from the right side, and the dorsal wall mainly from the left. Fig. 11 shows the heart-tube in process of formation, as indicated by a reconstruction of the stage of 36 somites; contact of the two sides has occurred at the posterior (arterial) end. The splanchnic mesoderm on each side (right particularly), for some little distance anterior to the contact area, shows evidence of preparation for bend- ing in the manner described above (Fig. IIC). Heart-tube forma- tion is now in rapid progress; the posterior (arterial) end now being complete, the venous end will be progressively formed, from behind forward, along an axis deviating to the left. The irregular black line in Fig. 11 indicates the outline of the endocardium; a small quantity of the latter has been included in the heart-tube. The heart shown in Fig. 11 (such as it is) is contracting rhyth- mically, and has been doing so for some 10 or 15 minutes. The heart which was quiescent at the stage of 35 somites began beating (after very little ])reliminarv oscillation) at a rate of 52 beats per minute, about 15 minutes before the thirty-sixth somite was com- pletely marked oflF.^^ It may be questioned whether the rhythmical contraction of the Water temperature G2° F. (July It, 1907). Some evidence has been obtained which suggests that in higher water temi)eratures the heart begins to beat at an earlier stage of develoi)inent (as estimated by the number of somites). In order to exclude the possibility of a miscount of somites the data on which this evidence rests require to be controlknl by comparison with the results of further observations, preferal)ly made on eggs of another species.