552 THE MEMBRANES 



origin rather to the intestine than to the bladder itself. But in 

 man and other animals furnished with incisors in both jaws, 

 and in whom the allantois is wanting, the size of the urachus 

 is so diminished, that although it rises from the fundus of the 

 bladder as a single tube, it afterwards splits into innumerable 

 fibres, which pass beyond the umbilicus together with the ves- 

 sels, and carry the urine into the chorion, although the exact 

 mode in which it does so cannot be demonstrated." On this 

 ground he accuses Arantius of a double error first, his de- 

 nial of the existence of the urachus in man; and, secondly, 

 his assertion that the foetus passes its urine through the geni- 

 tal organs. 



For my own part, I must confess I am a willing party to 

 the errors of Arantius, if errors they are to be called. For I 

 am quite sure, if pressure be made on the bladder of a full- 

 grown foetus, whether of man or of any other animal, that 

 urine will flow by the genitals. But I have never seen an 

 urachus, nor observed that the urine is propelled into the mem- 

 branes by making pressure on the bladder. I have indeed 

 seen in the sheep and deer what appeared to be a process of blad- 

 der between the umbilical arteries, and which contained urine; 

 but it in no way resembled the urachus as described by 

 Fabricius. Not that I would obstinately deny the existence 

 of an allantois; for the minor membranes are so delicate and 

 transparent (those, for example, which we have described as 

 existing between the two " \vhites" of the egg) that they may 

 easily escape observation. Moreover, in the hen's egg a white 

 excrementitious matter, and even faeces are found between the 

 colliquament and albumen, i. e. between the amnion and 

 chorion ; this I have mentioned before, and Coiterus has also 

 observed it. Added to which, the membrane of the colli- 

 quament itself, in which the foetus swims, although it is so 

 exceedingly transparent and delicate that Fabricius himself 

 allows nothing can be imagined more so, nevertheless (for accord- 

 ing to him all membranes, however thin, are double) may nature 

 sometimes find herself compelled to deposit urine or some other 

 matter between its duplicatures. An allantois of this kind I 

 am ready to allow Fabricius; but that other intestine-like body 

 produced into either horn of the uterus, I do not discover among 

 the membranes in cloven-footed animals, nor aught else, in 



