30 6 Dr. Davy on the urinary organs 
alligator. The shape of the kidney varies in different instances; 
to each ureter there is a papilla, and the papillae are situated 
in the receptacle itself ; and in no other respect have I been able 
to discover between the urinary organs of these lizards and 
of snakes, any material difference. Neither does the urinary 
secretion of these four species, and of many other species 
that I have examined, differ from that of snakes in its essen- 
tial nature ; in every instance I have found it nearly pure uric 
acid. The uric acid of the alligator contains a large proportion 
of carbonate and phosphate of lime. Two specimens of this 
urine, from different alligators, agreed in this circumstance ; 
they differed however in one having no odour, and the other 
a strong one of musk ; the former was from a very young, 
the other was from an older animal. 
3. Of the urinary organs and urine of the turtle and tortoise , 
The kidneys of the testudo mydas, and geometrica, the 
only species I have hitherto examined, resemble those of the 
preceding animals in their lobulated structure- The propor- 
tional size of the kidney of snakes is greatest ; that of lizards 
next; and that of the animals we are now considering, least. 
In the bladder, both of the turtle and tortoise, I have found 
flakes of pure uric acid,, but in no great abundance : it was in 
a transparent watery fluid, containing a little mucus and 
common salt, but no urea or any other substance that I could 
detect in the small quantity on which I operated. 
It is curious to observe the links by which animals, in ap- 
pearance totally dissimilar, are connected together. That 
there should be so close an analogy between the urinary 
organs and secretion of the serpent, lizard, and testudo, is 
