History of the development of the human ovum, with a comparative view of the development of the ova of mammalia and birds / translated and abridged from the German of Dr G. Valentin, of Breslau, by Martin Barry.

Date:: [1836?]

Credit: History of the development of the human ovum, with a comparative view of the development of the ova of mammalia and birds / translated and abridged from the German of Dr G. Valentin, of Breslau, by Martin Barry. 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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$surface with a circular boundary line, it is surrounded by a thick homogeneous layer of albumen, and furnished at both ends with the chalazas. In the isthmus, i. e. in that division of the oviduct, from the marked spot mentioned, to the beginning of the uterus, so called, the membrane of the egg-shell is formed around the ovum. As the isthmus is a straitened part of the oviduct, it becomes, as soon as the ovum has entered it, so dis- tended by the latter, that all folds of the mucous membrane dis- appear. This contributes probably, at least in part, to the se- cretion here, of a thin, but membranous layer, the membrane of the shell. The latter is found only so far on the ovum, as it has penetrated into the isthmus, which always happens with the pointed extremity first. Purkinje, who sacrificed more than thirty hens to his earlier researches, never found an ovum com- pletely in the isthmus, but only in part in the latter, in part passed out of it. Very recently, we were both so fortunate as to find an ovum just in the isthmus, and thence to inform our- selves of the manner in which the iTiembrane of the shell origi- nates. In the upper part of the isthmus, namely, there arises the fibrous layer of the membrane of the shell, which nature as it were, spins at once. There are found isolated threads, each of which is probably the seci'etion of a mucous follicle of the isthmus, which threads are the more frequent, and the more in- timately united, the deeper the part of the isthmus in which they lie. At the lower part, on the other hand, there is found in addition to this fibrous layer, a layer of granules, which oc- curs as a proper secretion. Besides this, there probably arises in the isthmus, the space filled with air found in the egg, and, indeed at a place where, immediately under the stricture of the isthmus, the folds of the mucous membrane are interrupted. From the isthmus, the ovum passes into the upper part of the uterus, where the shell originates, in the first place, through polygonal calcareous deposits, which continue to increase until they form a dense covering.—According to this representation, which rests entirely and solely upon observations, the ovum is taken up by the mouth of the tube. The first fourth of the i' oviduct secretes the membrana Dutrochetii, and the first rudi- j 1 ments of the chalazas,—the remaining part as far as the isthmus, the albumen,—the upper part of the isthmus, the fibrous,—the 1 lower, the granulous layer, of the membrane of the shell,—the j] greatest part of the uterus, finally, the egg-shell,—while the !' vagina is destined to perform the expulsion of the egg. The j '• bird's egg brought forth in this manner consists, when it is j I fresh and normal, of the following parts, \ l.Of the shell. 2. Of the membrane of the shell.$