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 fi-om 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. tioisUrgtn-llQiT bOB gc 



tioilooqan? 



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 

 tuberculated, 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 



