48 Dr Davy on the 



ago, I found this to be the nature of the urine of a large spe- 

 cies of frog, and of a toad which I examined in Ceylon.* 

 Lately, I have found the urine of the toad of this island (Bar- 

 badoes), which is of the same species as the common toad of 

 Europe (Raiia Oit/o), of lilve composition. 



What are the bearings of these facts in their physiological 

 relations ? Do they not prove that neither the temperature 

 of the animal, nor its activity, nor even its food (that is, the 

 physiological conditions connected with respiration, muscular 

 action, digestion, &e.), affect, materially, tlie nature, as to 

 composition, of the urinary secretion ? And does it not fol- 

 low that the quality of this secretion, therefore, must depend 

 chiefly on the intimate structure of the secerning organs 1 

 This is a view which, for a long while, has appeared to me 

 most consistent with established facts ; though, I believe, it 

 has never been generally adopted, and, recently, other views 

 have been taken, theoretically very different, which have been 

 supported by much ingenuity of reasoning, but not, I appre- 

 hend, equally by facts. 



I have spoken of the toad and frog as having a ui'inary 

 bladder. The function of the organ I allude to, and its pro- 

 per denomination, have, for a long wliile, been a subject of 

 difference of opinion ; some inquirers holding it to be a re- 

 ceptacle for urine, others, the receptacle of a fluid not derived 

 from the kidneys, but rather the product of cutaneous absorp- 

 tion. Even recently, I find that two English physiologists 

 maintain this latter opinion ; one of them seems to ground 

 it chiefly on the anatomical argument, that the vesicle, the 

 bladder of these animals, is the " unobliterated remains of 

 the allantois of the embryo, "t Granted that it is so, if it be 

 found to have inc^'eased in size with the growth of the ani- 

 mal, and to be so modified as to answer the purpose of a 

 urinary bladder, fitted to receive this fluid, and to let it es- 

 cape Avhen necessary, and that the fluid which is found in it 

 is actually of the nature of urine, as regards chemical com- 



* The results will be found in a paper published in the Philosophical Trans- 

 actions for, I believe, 1817, and in the first vi/luine of my Researches. 



t Professor Rymer Jones, in his '" General Outlines of the Animal Kingdom,' 

 p. 53.3. London, 1841. 



