AND PREGNANCY. 353 



cially towards its superior or internal orifice (544), so 

 that superfoetation, properly so called,* cannot natu- 

 rally take place. There are scarcely any constant and 

 infallible signs by which the woman herself can be 

 very certain of the changes that occur within during 

 conception.f 



564. The internal surface of the uterus becomes lined 

 with plastic, and, as it were, inflammatory, lymph (15), 

 which forms the tunica caduca or decidua of Hunter. J 

 This is said to consist of two laminae, — the erassa in- 

 vesting the uterus except at the orifices of the tubes 

 and of the canal of the cervix, § — and the caduca re- 

 jiexa, || so denominated from being, after the ovum 

 begins to be formed and to take root in the decidua, 

 continued over the other parts of the ovum, just 



* That different conceptions may occur from the repetition of copulation after 

 very short intervals, is proved by the instances of adulterous women who have 

 brought forth twins resembling different fathers in the colour of their skin : 

 viz. of black women who have brought forth a black and a mulatto, and of 

 European women who have brought forth a white and a mulatto. (B) 



f Ad. El. Siebold, De diagnosi conceptionis et graviditatls teepe dubia. 

 Wirceb. 1798. 4tr>. 



Gm. Thcopli. Kelch, De symptomatibus et signis graviditatis earumque 

 causis. Regiom. 1794. 4to. 



X Aretaeus Cappadox (De Causis et Sig. Morb. Diuturn. L. ii. C. ii. p. 64 sqq. 

 Boerhaave's edition) seems the first who gave a true account of the origin of 

 this membrane, the more accurate knowledge of which we owe to Wro. Hunter. 



After the revival of anatomy, Fallopius restored the knowledge of it. Observ. 

 Anat. p. 207. It is the chorion, either Bimply called so, or the spongy, tomen- 

 tous, fungous, filamentous, reticulated of the following age ; the involucrum 

 membranaceutn of Albinus. The first view of it was given, as far as my know- 

 ledge extends, by Ruysch. Thes. Anat. v. tab. i. fig. 1. F. B. C. G. 



§ W. Hunter, 1. c. tab. xxxiv. fig. 3 — 6. 



|| See B. S. Albinus, Annotat. Acad. L. i. tab. iii. fig. i, e, 



W, Hunter, 1. c. tab. xxxiii. fig. 1 — 4. 

 2 A 



