Natural History. 411 



not a trace could be found ; from which it would appear that the 

 peculiar substances present are the result of some change in the 

 principles of that body. 



M. Bracormot had also another specimen of urine for examina- 

 tion. It, by standing, deposited a minute quantity of blue matter. 

 He thinks also, that the specimen examined by M. Julia * must 

 have been coloured by this peculiar matter. — Ann. de Chimie f 

 xxix., 252. 



7. Analysis of an Urinary Calculus from a Hog. By M. Wiirzer, 

 of Marburg. — This concretion had been cut, in July, 1S24, at 

 Fulda, from the urethra of an emasculated pig, under a twelve- 

 month old. It had the size and shape of a small bird's egg. It 

 weighed 91 grains. Its specific gravity was 1.964. It was 

 covered by a thin light-gray crust, and when broken, presented a 

 radiated and concentric crystallization. Upon chemical examina- 

 tion and analysis, it was found to contain the following substances 

 and proportions. 



Phosphate of lime and ammonia . 51.7S7 



Muriate of potash . . . 2.625 



Protoxyde of iron . . . 0.169 



Slimy matter, with a urinous smell . 1.648 



Water . . . .43.573 



Loss . . . . 0.198 



100.000 

 Phil. Mag., lxvi., 2S8. 



8. Chinese Marnier of forming Artificial Pearls. — Mr. Gray's 

 observations upon the artificial production of pearls are inserted 

 at page 167 of our last volume. In a late visit to the College 

 of Surgeons, Mr. Gray observed some pearls in the same spe- 

 cies of shell before spoken of (Barbala Plicata,) which had the 

 external appearance of having been formed artificially. These 

 pearls are described as of a very fine water, and nearly orbicular ; 

 their base is supported by a small process, which separates at the 

 vud into two short diverging processes, which stand off at right 

 angles to the central rib. On more minute examination, it ap- 

 peared that they had been produced by the introduction be- 

 tween the mantle of the animal (while yet alive) and the shell, of 

 a small piece of silver wire, bent into a peculiar form; that is to 

 say, so as to form a right angle, with one arm ending in two 

 diverging processes, so as to make the simple end always keep its 

 erect position. These wires must have been introduced in the same 

 manner as the semi-orbicular pieces of mother-of-pearl in the 

 other method of forming artificial pearls, as there is no appear- 



* Quarterly Journal, XVI. p. 1 17. 



