578 PHILOSOPHICAL TRANSACTIONS. [aNNO 1701. 



ene of the coats of the amnios. Whereas having first found the opening whence 

 the urine issued, if the allantois is not too much torn, you may blow up the 

 allantois with a blow-pipe to its full dimensions, and then see its true shape, the 

 fundus, the cervix, the insertion there of the urachus, and its relation to the 

 other membranes, &c. Be the allantois ever so much torn, yet this way you 

 may easily separate many inches of it from the chorion and amnios. Which 

 easy separation demonstrates a distinction of membranes, since no double mem- 

 brane can be divided by the breath alone. 



Indeed Hoboken and Diemerbroeck make it a very easy thing to separate the . 

 allantois from the other membranes only by the fingers ; but it is plain from 

 their descriptions that they never saw one entire. Among other mistakes, 

 Diemerbroeck says that the urine of a foetus lies between the urinary membrane 

 and the chorion ; as though not contained in a distinct bladder, but in a cavity 

 made partly from the chorion, partly from the urinary membrane. 



It is true De Graaf tells us, that by blowing with a pipe into a hole made 

 through the chorion, all the membranes of the secundines will appear distinct. 

 He has also delineated an allantois with the other membranes, &c. as he found 

 them : yet this fig. must have been drawn from his own fancy, and not from 

 any preparation ; and that for these reasons. 1st, Because by this way of sepa- 

 ration you can only part the allantois from the chorion, but never see its true 

 dimensions, nor any appearance of a bladder ; for a bladder, as the allantois is, 

 can be shown only by blowing into its cavity, or by finding it full. Yet in this 

 fig. no sign can be observed where it was blown up and tied. Nor can this 

 allantois be supposed full of urine, because it is not of the shape of a full allan- 

 tois, and he himself calls it only the inflated part of the allantois. However I 

 cannot conceive how the allantois could remain partly filled with air, any more 

 than it might with urine, so long as till this fig. was drawn, unless some hole 

 was tied up whence the urine issued, and the air was blown in. 2dly, Because 

 in this fig. the umbilical cord seems to run through both amnios and the allan- 

 tois, to its insertion on the placenta. Whereas the allantois is no where per- 

 forated by the umbilical cord, nor does it any where pass through the amnios, 

 but only runs under it, at the place of its insertion on the placenta. If the 

 navel-string could be allowed to enter the amnios, and to pass under it to the 

 placenta, why should it not appear (which it does not) under the amnios, as 

 well as the thin substance of the allantois ? Again, according to De Graaf's 

 position of the secundines, nothing could hinder a plain view of the place where 

 the navel-string is attached to the placenta. Tiiis will be easily a[)prehended, 

 by supposing the part h in my first fig. to lie uppermost, the fundus g, and 

 navel-strings being turned over ; for then the strings will run over the allantois 



