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VIII. An Account of the urinary organs and urine of two species 
of the genus Rana. By John Davy, M. D. F. R. S. 
Read January 18, 1821. 
In a letter to Sir Humphry Davy, which was written almost 
two years ago, and which I understand has been honoured 
with a place in the Transactions of the Royal Society, I have 
described the kidneys of many different animals of the class 
Amphibia, and have shown, with one exception not there 
insisted on, that their urinary secretion is very similar, con- 
sisting almost entirely of uric acid, 
The exception which occurred to me, was in the case of 
frogs, on whose urinary organs and secretion I have had 
an opportunity, lately, of making fresh and more minute en- 
quiry, the results of which I beg leave to communicate. 
I shall first relate the observations I have collected on the 
urinary organs of these animals, and then describe the ex- 
periments I have made to determine the nature of their urine. 
The examination I have engaged in, has been limited to 
two species, the bull-frog (Rana taurina, Cuv. ) and the 
brown-toad (Bufo fuscus, Laurenti) which are both very com- 
mon in this neighbourhood ; the former inhabiting the lake 
of Colombo, where it occasionally grows to a great size ; and 
the latter frequenting houses, and abounding by night in the 
streets of the Pettah. 
The kidneys of the bull-frog are apart, one on each side of 
