MORBID CONCRETIONS. 



cystin* was first described and examined by Dr Wollaston.f 

 Calculi composed of it have a pale yellow colour, are translucent, 

 and appear irregularly crystallized. It was analyzed by Dr 

 Prout, and found composed of C 12 H 12 Az 2 O 16 . It is, therefore, 

 probably related to oxaluric acid. Being, in fact, two atoms of 

 oxaluric acid -f- eight atoms water + one atom azote. 



Stromeyer found cystic oxide in the gravel passed by a pa- 

 tient. The urine of this patient contained a good deal of cystic 

 oxide, but hardly any uric acid ; and the urea was not in its na- 

 tural state.J 



10. Xanthic oxide calculi. Only two specimens of this very 

 rare calculus have been hitherto observed. Dr Marcet first de- 

 scribed it from a specimen from Drs Babbington and Wdhler, 

 and Liebig analyzed it from a much larger calculus extracted 

 from a patient by M. Langenbeck, and still preserved in Lagen- 

 beck's collection. They found its constituents C 10 H 4 Az 4 O 6 . 

 Now uric acid is C 10 H 4 Az 4 O 8 . It differs, therefore, from the 

 xanthic oxide of Marcet, by containing two atoms more oxygen. 

 Hence the reason why Wohler and Liebig have given it the 

 name of uric oxide. It is even much rarer than cystic oxide ; 

 since only two calculi composed of xanthic oxide have been 

 hitherto discovered. 



11. Fibrinous calculi. Only a single calculus of this kind has 

 been hitherto met with. It was about the size of a pea, and was 

 given by Sir Astley Cooper to Dr Marcet. 



It had a yellowish-brown colour, somewhat resembling bees'- 

 wax. Its hardness was also nearly that of bees'-wax. Its surface 

 was uneven, but not rough to the touch ; its texture rather fibrous, 

 and the fibres apparently radiating from the centre. It was some- 

 what elastic. It burnt with flame, emitting an animal smell, which 

 did not resemble that of uric acid, cystic, or uric oxide calculus. 

 It was insoluble in water and in muriatic acid, but it formed a 

 soapy solution with caustic potash, from which it was precipitated 

 by muriatic acid. Nitric acid dissolved it, though not very rea- 

 dily, and the solution when evaporated to dryness did not leave 

 a red or yellow stain. When boiled in very dilute nitric acid, 

 it swelled to a great size, and was at last dissolved. The solu- 



* See page 105. f Phil. Trans. 1810, p. 223. 



| Ann de China, et de Phys. xxvii. 221. 



