ureters through which the urine distils, a fact which was un- known to Aristotle and philosophers up to this time. In birds and serpents, which have spongy or largely vesicular lungs, the quantity of urine secreted is small, because they drink little, and that by sipping; there was, therefore, no occasion for an urinary bladder in these creatures : the renal secretion, as already stated, is accumulated in a common cavity or cloaca, along with the drier intestinal excrement. Nevertheless, I do find an urinary bladder in the carp and some other fishes.
In the common fowl the ureters descend from the kidneys, which are situated in long and ample cavities on either side of the back, to terminate in the common cavity or cloaca. Their terminations, however, are so obscure and so hidden by the margin of the cavity, that to discover them from without and pass a fine probe into them would be found impossible. Nor is this at all surprising, because in all, even the largest animals, the insertion of the ureters near the neck of the bladder is so tortuous and obscure, that although the urine distils freely from them into the bladder, and calculi even make their way out of them, still neither fluids nor air can be made to enter them by the use of any amount of force. On the other hand, in birds as well as other animals, a probe or a bristle passed downwards from the kidney towards the bladder by the ureters, readily makes its way into the cloaca or bladder.
These facts are particularly distinct in the ostrich, in which, besides the external orifice of the common cavity which the velabrum covers, I find another within the anus, having a round and constricted orifice, shutting in some sort in the manner of a sphincter.
Passing by these particulars, however, let us turn to others that bear more immediately upon our subject. The uterine outlet or vulva, then, or the passage from the common cavity to the uterus of the fowl, is a certain protuberance, soft, lax, wrinkled, and orbicular, resembling the orifice of the prepuce when closed, or appearing as if formed by a prolapse of the in- ternal membrane of the uterus. Now this outlet is situated, as I have said, between the anus and rump, and slightly to the left of the middle line of the body, which Ulysses Aldrovandi ima- gines to be for the purpose of " facilitating intercourse, and the entrance of the genital organ of the cock." I have myself ob-
