Urinary Secretion of certain Animals. 47 



5. Lizards, with a temperature like that of serpents, and, 

 like them, living entirely on animal matter, resemble them 

 also, so far as my experience allows me to speak, in the com- 

 position and quality of their urine. The trials I have made 

 of it have been limited to that of three or four different spe- 

 cies. 



6. The frog and toad, both of very low temperature, living 

 entirely on animal matter, and capable of long continued 

 fasts, have a urinary secretion different from that of any of 

 the preceding. In all the preceding instances, this secretion 

 Avould appear to pass from the secerning organs, — the kidneys, 

 — in a semifluid state (granules of lithate of ammonia, mixed 

 with a little watery fluid), and to become solid before it is 

 voided, or shortly after, in consequence of the absorption of 

 the aqueous part in the cloaca serving as a urinary recep- 

 tacle, or its loss by evaporation in the open air. But, in the 

 instance of these Batrachian animals, it is secreted by the 

 kidneys, in a liquid state, and very dilute, and is commonly, 

 after passing into the cloaca, received into a very thin, and 

 dilatable, and contractile bladder, which communicates by a 

 large longitudinal opening, provided with a valve,* with the 

 lower part of the intestinal canal, — the cloaca, — in which the 

 waters terminate. t The dilute liquid urine of these animals 

 consists chiefly of water holding, in solution, urea and a little 

 saline matter, and, in its composition, may be considered as 

 an approach to the human urinary secretion. Many years 



* I am not aware that the valvular structure alluded to above has yet been 

 described ; it is a sciiiiluna fold of the delicate liniig membrane of the cloaca, 

 extciiUiiig across, not unlike the valve of a vein in its form, and, in position, in 

 regard to the opening into the bladder, not unlike that of epiglottis in relation 

 to the glottis. Wlien pressed down, as by the pressure of a probe moved to- 

 wards the anal opening, it completely covers the aperture into the bladder. It 

 is perfectly well adapted to allow a fluid, descending from the waters, to pass 

 when the sphincter ani is closed, and to prevent fo:;cal matter from entering the 

 bladder in its descent through the cloaca, where it never lodges, a sphincter 

 above keeping it in tlie largo intestine. 



t As difference of opinion exists amongst high authorities in comparative 

 anatomy relative to the termination of the waters of tliese animals, 1 may men- 

 tion tliat I have passed a fine leaden probe through the water of tlie toad into 

 its cloaca. 



