Some deductions from a study of the development of the heart / by G. A. Gibson and A. L. Gillespie.

Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Some deductions from a study of the development of the heart / by G. A. Gibson and A. L. Gillespie. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    OF THE DEVELOPMENT OE THE HEART. A CONSIDERATION of the physical problems arising out of cases in which, on account of the retention of certain embryonic arrange- ments, deviations from the normal relative pressures existing in the systemic and pulmonic vessels are present during adult life, has led us to seek some means by which it might be possible to establish a basis upon which we may rest with certainty in rea- soning upon such conditions. As it seems probable that in the anatomical relations of the two sides of the heart during foetal life such a secure foundation may be obtained, we have examined the heart of the embryo in order to ascertain the anatomical conditions existing at different stages of its development. During foetal life the pressure on both sides of the heart must be nearly equal, on account of the free communication allowed by means of the ductus arteriosus and foramen ovale ; and it might, a priori^ be expected that the walls of the ventricles on the two sides of the heart should he of approximately equal thickness. This expectation we found to be in great part justified by our results, as will be seen in the sequel. Before entering upon the observations which we wish to lay before the Society, it may be of use to sum up, as briefly as possible, the course of events in the development of the central vascular apparatus. The vascular system makes its first appearance in the form of two simple lateral tubes in the anterior part of the embryo. These tubes occupy spaces which are continuous with the pleuro-peri- toneum, and are composed of two layers apparently developed respectively from the mesoblast and hypoblast. Each tube is con- tinuous in front with the cephalic mesoblast, and terminates behind in the omphalo-meseraic or vitelline veins. These lateral tubes are developed in the part of the embryo which, on the folding downwards of the body-walls, becomes the ventral wall of the pharynx ; and when this wall is completed they meet in the middle line and become fused into a single tube. This remains connected with the vitelline veins behind, and bifurcates in front, giving rise to the primitive aortae.