PLACENTA. 189 



it at a certain distance from each other, they will each have a dis- 

 tinct placenta, chorion and amnios, and sometimes even an epicho- 

 rion, until a certain stage of the gestation. If, on the contrary, they 

 had already contracted some adhesion together previously to leaving 

 the Fallopian lube, or if they happen to remain very near each other 

 in the uterus, it may be that they shall be enclosed in one single leaf 

 of the deci.lua, and that their villi, as well as their chorion, shall be 

 early confounded together. In this case it may be that the septum 

 formed by their conjunction, shall give way, and cause the two 

 foetuses to be found enclosed at birth in one single bag of membranes, 

 numerous instances of which are related in the scientific collections, 

 and of which one of the most authentic has been recently laid before 

 the public by Madame Boivin. Nevertheless, such a circumstance 

 is of very rare occurrence, for in double after-births, I have always 

 succeeded in tracing the chorion and amnios to the intermediate 

 septum, where the two membranes were more or less promptly con- 

 founrled, and in a more or less intimate degree. In general, the 

 vessels of the two placentae do not communicate with each other, 

 any more than the vessels of the different lobes of the same placenta; 

 but it is easily conceived that the contrary may take place some- 

 times, as seems to be demonstrated by facts carefully examined. 



ARTICLE II. 

 Of the Foetus. 



486. The ancients retained the name yovri, seed, for the product 

 of conception for the first six days. During the next nine days they 

 called it xnjjfta, then embryo for twelve days, after which they made 

 use of the term ■cahvov, to designate the fcetus until the forty-fifth day, 

 and these four supposed periods were characterised by them in the 

 two following verses: 



Sex in lacte dies, ter sunt in sanguine terni, 

 Bis seni carnem, ter seni membra figurant. 



At present it is generally agreed to give to the germ, when with- 

 out its membranes, the name of embryo, until the third month of 

 pregnancy; or according to some, until its several parts can be dis- 

 tinguished from each other; it is afterwards called /tt/ws as long as 

 it remains in the womb, and the term child is not applied to it until 

 after its birth. Although this division is entirely arbitrary and diffi- 

 cult to justify, I feel bound partially conform to it in this work. 



17* 



