554 MORBID CONCRETIONS. 



and Bergman till Dr Wollaston published his important paper 

 on urinary and gouty concretions in 1797. Mr Lane, indeed, 

 examined the action of heat on various calculi, and the quantity 

 of each dissolved in 48 hours in caustic potash.* About the year 

 1797, Brugnatelli published some observations on urinary calcu- 

 li.! Those which he examined he found partly soluble in water, 

 and he says that the portion dissolved was biphosphate of lime. 

 The portion not soluble in water was uric acid, and he says that, 

 when treated with nitric acid, a great part of it was converted 

 into oxalic acid. 



Dr Wollaston, in his paper published in the Philosophical 

 Transactions for 1797 (p. 386), describes four new species of 

 calculi, which had been observed indeed before, but their chemi- 

 cal constitution was unknown till it was determined by Wollas- 

 ton. These were, 1. Fusible calculus. It had been observed by 

 Smithson Tennant, that when this calculus was exposed to the 

 action of the blowpipe, instead of being consumed like the uric 

 acid calculus of Scheele, it left a considerable residue, which fused 

 into an opaque white glass. Wollaston found that these calculi 

 contained brilliant crystals of ammonia-phosphate of magnesia, 

 which were usually mixed with phosphate of lime and some uric 

 acid. 2. Mulberry calculus. This name had been given by sur- 

 geons to a dark-coloured calculus with an uneven surface, bear- 

 ing some resemblance to a mulberry. Hence the name. Dr 

 Wollaston found that it consisted essentially of oxalic acid com- 

 bined with lime. The smooth calculus known by the name of 

 hemp-seed calculus, W ollaston found also to be chiefly oxalate of 

 lime ; but to contain phosphate of lime and some uric acid. 

 From the late investigations of Wohler and Liebig, it seems to 

 be very probable that the mulberry calculus is in reality a com- 

 pound of oxaluric acid and lime. 3. Bone earth calculus. This 

 calculus has a brown colour, is smooth, and composed of concen- 

 tric laminae, easily separated from each other. Before the blow- 

 pipe it is at first charred ; then becomes perfectly white, and 

 urged by the utmost heat of the blowpipe it fuses. It consists 

 essentially of phosphate of lime ; and differs from bone earth by 

 containing no carbonate of lime. 4. Calculi from the prostate gland. 

 These are small calculi having the colour and transparency of 



* Phil. Trans. 1791, p. 223. t Ann. de Chim. xxviii. 52, 



