460 MORBID PEODUCTS. 



picted in fig. 25, and the oxalate in minute globules, or in 

 oetohedra, as represented in fig. 36. Phosphate of lime and 

 ammoniaco-magnesian phosphate almost always occur together; 

 oxalate of lime sometimes occurs by itself, and sometimes alter- 

 nates with the earthy phosphates. Gravel consisting principally 

 of the earthy phosphates is sometimes mixed with urate of 

 ammonia, which latter readily dissolves when heated in water. 



I have alluded to the analysis of this kind of gravel in my 

 remarks on urinary sediments in p. 181. The urine in which 

 this white earthy gravel is formed, is either neutral or alkaline, 

 never acid. 



Magendie describes a species of gravel containing hairs, 

 (gravelle pileuse), consisting of phosphate of lime, ammoniaco- 

 magnesian phosphate, and a little uric acid. It is possible 

 that the hair may have been introduced from without, and 

 thus be a mere accidental constituent. When cystin occurs 

 as gravel, it almost always assumes the regular crystalline form 

 that is so characteristic of that substance. Cystic gravel is of 

 a yellow colour, and appears crystalline even to the naked eye. 



Lecanu 1 analysed Segala's collection of 110 specimens of 

 gravel. Seventy-nine of them (passed by 20 patients) con- 

 sisted of uric acid with traces of ammonia and organic matter, 

 which, however, in five cases were found only in the cortex, 

 the nucleus consisting of pure uric acid. One minute calculus 

 passed at the same time with others of pure uric, had a nucleus 

 of oxalate of lime, and a thick cortex of uric acid. Five calculi 

 from different patients, consisted of oxalate of lime without 

 earthy phosphates, but with some uric acid ; nine from different 

 patients consisted of oxalate of lime and earthy phosphates; 

 three from two patients consisted of phosphate of lime and 

 ammoniaco-magnesian phosphate, without uric acid ; four from 

 the same patient consisted only of earthy phosphates; four 

 from two patients consisted of ammoniaco-magnesian phosphate, 

 without any appreciable traces of lime; three from two patients, 

 of cystin. A calculus, the size of a pea, discharged with uric 

 acid gravel from a man aged 62 years, was soft and white, 

 soluble in water and alcohol, fusible, when heated evolving an 

 odour of burned sugar, and containing a brown nucleus, formed 



1 Journal de Pharmacie, Sept. 1838. 



