On the physiology of the embryonic heart : being a thesis for the degree of Doctor of Science of the Universty [i.e. University] of London, 1893 / by J.W. Pickering.

  • Pickering, John William.
Date:
1893
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Licence: Public Domain Mark

Credit: On the physiology of the embryonic heart : being a thesis for the degree of Doctor of Science of the Universty [i.e. University] of London, 1893 / by J.W. Pickering. 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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    liable to lead to error than the results obtained from the study of a single class of animals. Histoi'ical Siimmari/ of previous tvorlc on the Embryonic Heart. The phenomena of the embryonic heart have been observed since the earliest times, since Aristotle(i) mentions the “ a-rtjfir] Ktvovjjbhr} in the hatching hen’s egg. Hieronymus Fabricius(2) figured in his treatise on the incubation of the hen’s egg, the area vasculosa. Harvey(3) wrote of the embryonic heart “about the end of the fourth and the beginning of the fifth day, being now enlarged, it seemeth to be changed into a small thin bladder containing blood which it ejects at every contraction and recalls at every diastole.” He further found that touching the heart either caused it to beat faster or stopped it altogether, a fact which has been recently confirmed by Sonnenkalb. He also observed that cold delays and finally stops its beating and that on warming it “presently gaineth strength and vigour.” Langley(^) described two moving points at the centre of the vascular area of the embryo. This was confirmed by Maitre Jean(5) and by Lancisi(6), who worked under Malpighi’s direction. Vieussens(7) pointed out what previous observers had (excepting Harvey) not noticed, viz., the morphological identity of the moving embryonic points with the adult heart. He also laid stress upon the importance of the elasticity of the cardiac muscular fibres in considering the causes of the rhythm of the heart, a factor which has recently been brought into notice by the researches of Roy (8). The subject was more fully investigated by Haller(9), who used the evidence of the embryonic heart in support of his famous doctrine that the rhythmic contraction of the cardiac fibres depends on their inherent irritability. To those who stated that the systolic phase of the heart cycle was due to compression of the nerves, he answered “in fish, and in little chicklings in the egg there can be no room for a compression of the nerves. He first observed the embryonic heart beat at 45 hours. Von Baer(iO) and Remak(H) observed it at about the same period of incubation, while Prdvost and Dumas(l2) saw it at the 36th or 39th hour. Von Baer observed that the first contractions of the embryonic heart were irregular, but this was thought by His(i3) to be due to the younger embryos being more infiiienced by cold than those more mature.