354 OF CONCKFTION 



i 



as the peritonaeum is continued over the abdominal 

 viscera. 



565. The ovum* is produced before the embryo which 

 it is intended to contain, but scarcely begins to be 

 formed earlier than the end of the second week from 

 conception. Previously to this period, I very much 

 doubt whether any vestige of human conception has 

 ever been visible. (C) 



566. This ovum consists, besides the external acces- 

 sary covering afforded by the caduca of Hunter, of two 

 proper velamenta or membranes. 



Of an exterior — the chorion^ of the moderns, the 

 external surface of which is, from the first, nearly 

 covered with inexpressibly beautiful knotty flocculi; 

 whence it has been called the flocculent, leafy, or 

 mossy, chorion. By means of these flocculi, which are 

 the rudiments of the foetal portion of the future pla- 

 centa, the ovum takes root, as it were, in the uterine 

 decidua. (564) 



Of an interior — styled amnion, possessing no blood- 

 vessels (5), delicate, but remarkably tough. 



567. These two proper membranes of the ovum differ 

 very much from each other in size the first week after 

 the formation of the ovum ; the chorion appears a large 

 bladder, to which the amnion, like a much smaller 



* Respecting the membranes of the ovum and their connection with the 

 uterus and embryo, vide J. F. Lobstein, fiber die ErnShrung det Fetus. Halle. 

 1804. 8vo. 



f The Membrana media of Rouhault, Haller, &c. For the various synonyms 

 and homonyms of the membranes of the ovum, consult Haller, Eletn. Physiol. 

 Vol. viii. P. i. p. 194 sq. and Tabarrani's letter to Bartoloni, Atti di Siena. 

 T. vi. p. 224 sq. 



