TENDENCY TO CALCULOUS DISEASES. 
77 
must be particularly directed to the circumstances under which lithic acid is 
formed, or developed. The importance of this attention is put in a very striking 
point of view by Dr. Prout, when he says, “ that if a lithic acid nucleus 
had not been formed and detained in the bladder, two persons at least out of 
three who suffer from calculus, would never have been troubled with that 
affection.” 
A deposition of the phosphates, is not, according to Dr. Prout’s experience, 
followed by that of the other materials of calculi ; and in this important par- 
ticular, my observations, with hardly an exception, agree with his. Sometimes, 
indeed, I have seen little studs of lithic acid, or lithate of ammonia, imbedded 
in the mixed phosphates ; but these appear to have descended from the kidney, 
as small calculi, and to have attached themselves to the phosphates during 
their existence in the bladder ; for the laminated form which those phosphates 
often assume, is not interrupted under such circumstances, but only slightly 
altered in direction. Notwithstanding, however, the well marked character of 
the different species of urinary calculi, or their varied laminae, there is still 
hardly a single deposit, with which a small portion of some of the other ingre - 
dients is not blended ; a circumstance which probably arises, (as in the case of 
muriate of ammonia) from the readiness with which urine parts with a minute 
portion of most of its component parts. 
Of oxalate of lime. 
The calculus of oxalate of lime, has been generally designated as the mul- 
berry calculus, from its resemblance, both in shape and colour, to a mulberry. 
Its appearance, however, varies from the darkest brown to a milk white, not 
differing much in colour from the fusible calculus. Its texture is generally 
tuber culated, or nodular ; but this substance not unfrequently exists, in bright 
amber-coloured, or transparent white crystals, of the shape of flattened octo- 
hedrons. This form was noticed by M. Fourcroy, in concretions taken from 
the bladders of some animals, and was particularly observed by Dr. Wollaston, 
in three human calculi shown him by Dr. Marcet. There are not less than 
twenty examples, in the Norwich collection, of such crystallization : and I have 
seen a few examples elsewhere. — I had occasion to observe a similar form of 
crystal, in two or three small calculi of oxalate of lime, taken from the bladder 
