AND HUMOURS. 553 



fact, except the conception itself. I can only find, as I before 

 said, a process of the bladder, situated between the umbili- 

 cal arteries, which contains an excrementitious matter, and 

 varies in length in different animals. Wherefore, in my opinion, 

 the tunic which Fabricius calls the allantois is, in fact, the 

 chorion j and the ancients applied the name of allantois to it 

 on account of its resemblance to a double intestine. For that 

 external membrane, constricted in the middle, and resembling 

 a saddle-bag in form, which is stretched upwards to each horn 

 of the uterus, and in its passage is pinched in by that part 

 of the uterus which connects the horns, is in truth the cho- 

 rion ; and in the sheep, goat, roe, fallow-deer, and other 

 cloven-footed animals, it can be raised by the hand in the mid- 

 dle of its course, and easily extracted whole ; this is the same 

 as what is called the " conception" or ovum. Like an egg, it 

 contains within itself two fluids, and the foetus with its appen- 

 dages ; it is possessed besides of those characters which Aristotle 

 attributes to the egg; these are, that out of part of it the embryo 

 is originally formed, and that the remainder constitutes the sus- 

 tenance of the new animal, as has been frequently explained. I 

 believe, then, the tunic which Fabricius called the allantois to be 

 either the chorion or else some unnatural structure formed 

 out of the reduplication of the membranes. It is accordingly 

 only found to exist in some animals, and not always in these; it 

 cannot be traced from the commencement of conception, and in 

 some animals it is more apparent than in others: whilst in others 

 nothing can be seen except a mere process of the bladder. 

 Besides, Fabricius himself allows that its purpose is not to en- 

 velope the foetus, but to contain its urine. In truth, I must 

 think that he has described it rather to defend the doctrine of 

 the ancients, than because he really believed he had discovered 

 such a membrane, or that it served any good purpose. For 

 he allows, with the ancients, and every medical school, that 

 the chorion contains urine, when he says l that there are 

 t\vo humours encircling the foetus, one, viz. in the amnion, 

 consisting of sweat; the other in the chorion, consisting of 

 urine. It is, therefore, clear that the ancients under the two 

 names understood one and the same membrane; and that in 



Cap. i. 



