266" PHILOSOPHICAL TRANSACTIONS. [ANNO 1798. 



the minutest proportion of the above animal oxide in urinary concretions, and also 

 in other substances, but even to determine its proportion to the other constituent 

 parts, in the space of a few minutes, in most cases, and in all in a very little time, 

 without any other apparatus than nitric acid, a round bottomed matrass or glass 

 dish, and a lamp. By this method, I have, in a general way, examined above 300 

 specimens of concretions, of the human subject and other animals, principally 

 urinary ones; and also many from other parts, particularly those from the joints. 

 For these opportunities I am beholden to several professional gentlemen; whose 

 willingness to furnish me with specimens, I shall have much satisfaction in acknow- 

 ledging on a future occasion. At present, I must acknowledge my obligations to 

 Mr. Heaviside, in whose museum I found between 700 and 800 specimens. The 

 liberal possessor of this treasure offered me, what I could not have taken the 

 liberty of requesting, viz. permisson to break off pieces from any of the articles, 

 for experiment. Mr. Edward Howard did me the honour to take on himself the 

 task of writing down the reports, and otherwise assisted me. At this time I shall 

 only mention, 1. That out of 200 specimens of urinary calculi, not more than 6 

 did not contain the animal oxide above described, i. e. about 32 out of 33 con- 

 tained it. 2.- That the proportion of this oxide was very different; varying from 

 ^±^ exclusive of water, to -£-§-§•; but, for the most part, varying between -^VV and 

 ■^«g.* 3. That the common animal mucilage of urine is frequently found in con- 

 cretions, in very different proportions; but is perhaps never a principal constituent 

 part of them. 4. That the above animal oxide was not found in the urinary concre- 

 tions, or any other concretions, of any animal but the human kind. 5. That 

 this animal oxide was found also in human arthritic calculi, but not in those of the 

 teeth, stomach, intestines, lungs, brain, &c. 



p. s. I think proper to subjoin a few experiments, made after the preceding 

 paper was written, which afford evidence of the truth of some of my conclusions, 

 and enable us to explain several properties of animal concretions. 



1. On a urinary concretion from a dog. — This calculus may be said to be a great 

 curiosity, for it is probably the only specimen in London. I owe the opportunity 

 of examining it to Mr. H. Leigh Thomas, who met with it in the course of his 

 dissections ; and therefore we have unquestionable authority, that the concretion 

 was really from the urinary bladder of a dog. It is worthy to be noticed, that the 

 animal appeared to be in perfect health. This concretion is of an oval figure; is 

 3-f- inches in length, and 3 inches in breadth; is white as chalk; its surface is 

 rough and uneven. Being sawed through longitudinally, no nucleus was found, 

 nor was it laminated, but near the centre it was radiated, and contained shining 

 spicula. In other parts it was, for the most part, compact and uniform in its tex- 

 ture. It weighed nearly 10-J- oz. Its specific gravity was found to be greater than 



* In some urinary concretions, the interior part contained this oxide, and the exterior parts had none 

 of it. On the contrary, in other urinary concretions, the exterior part contained it, and the interior 

 part did not. — Orig. 



