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IX. On some New Sjiccies of Animal Concretions. 

 By Thomas Taylor, Surgeon. 



To Richard Taylor, Esq. 

 Dear Sir, 

 \ S the Catalogue of the Calculi belonging to the Royal 

 ■*"*■ College of Surgeons has now been published some 

 months, and there consequently remains no further necessity 

 for silence, I purpose in the following paper to redeem the 

 promise I formerly made, of describing some of the more re- 

 markable of the concretions which have been discovered du- 

 ring the examination of that very large collection ; and also 

 to detail the experimental proofs on which the assertions as 

 to their composition were founded in the short notice which 

 you did me the favour of inserting in this Journal in May 

 1844. 



I do this the more willingly, as it was considered advisable 

 to omit the details of the analyses in the Catalogue. More- 

 over, the Catalogue having but a limited circulation, many of 

 the new facts that have been elicited would not otherwise be 

 generally known. I shall, however, confine myself in this 

 paper to the notice only of such concretions as are entirely 

 new, or whose composition has been either imperfectly or in- 

 correctly described. For the historical account of the succes- 

 sive steps by which our present knowledge of these bodies has 

 been obtained, and for the description of the more common 

 species of calculi, I must refer to the Catalogue itself. 



Urinary Calculus from the Iguana, consisting of Urate of 



Potass. 



Small and unimportant quantities of urate of potass may 

 occasionally be detected in human urinary calculi, but no in- 

 stance of this salt constituting an entire calculus has hitherto 

 been described. There are three specimens of this description 

 in the College collection, which resemble each other in every 

 respect save in size. Two of them were described in the MS. 

 Catalogue of Sir Hans Sloane's collection as " Piedra de 

 Yguana,"and there is little doubt but that they were taken from 

 the urinary bladder of some of the large Iguanas or tree lizards 

 of South America. The other concretion had no history, but 

 had been described as "a mixed calculus in which uric acid 

 predominates." Although much larger, it was so similar in 

 composition and general appearance to the others, that there 

 does not appear any reason to doubt its having a similar ori- 

 gin. In their external characters these concretions resembled 

 calculi composed of the mixed phosphates, being made up of 



