TENDENCY TO CALCULOUS DISEASES. 73 



of the calculus, as indicated on the addition of pure potash ; though there is 

 not, except occasionally towards the centre, the laminated structure of early 

 life. In a few instances, the appearance of the lithate of ammonia calculus is 

 not very dissimilar to the chalk-like excrement, or rather urine of the Boa Con- 

 strictor, which, as is well known, consists of lithate of ammonia*. 



Immersion, for a few days, in pure ammonia, converts yellow laminated 

 lithic acid, whether in small masses, or in powder, into light-coloured lithate of 

 ammonia, from which ammonia is readily evolved by the action of pure potash, 

 after that which is loosely adherent, has been carefully separated by distilled 

 water. But the artificial addition of ammonia does not, as far as I have ob- 

 served, communicate any degree of decrepitation to a lithic calculus, as might 

 be imagined from an observation of Dr. Prout. It seems to be exceedingly 

 likely, that some, at least, of the specimens of lithic calculus, which gave rise 

 to Scheele's discovery of lithic acid in urinary calculi, really consisted of lithate 

 of ammonia ; since we are informed, that in his original expei'iments, a disen- 

 gagement of ammonia took place, during the solution of the subjects of his 

 analysis in liquid caustic potash, which would not have been the case, if the 

 lithic acid, on which he operated, had been pure and uncombined-f-. 



♦ Dr. Prout states to me, that he has never seen a calculus, essentially of lithate of ammonia, 

 taken from a person after puberty ; and is of opinion, that there are at least two varieties of the com- 

 bination of lithic acid with ammonia, if not more. — It is exceedingly likely, that it is owing to the 

 different quantities of ammonia, with which lithic acid, according to this very probable idea, is capa- 

 ble of being combined, with some diversity, perhaps, in the admixture of other substances, that the 

 varieties observable in the appearance of lithate of ammonia, in calculi, are to be attributed. 



I have had occasion, since this paper was laid before the Society, to examine some very minute 

 round calculi, which were put into my hands by Mr. Dalrymple, now senior surgeon to the Norwich 

 Hospital. They were 59 in number ; were passed by a clergyman of about 54, all at once ; and 

 though they amounted only to three-eighths of a grain in weight, they occasioned considerable suffering 

 prior to their discharge. They were amorphous in the centre, and laminated externally ; and 35 were 

 of very pure yellow lithic acid, the remaining 24, of gray lithate of ammonia, very similar in appear- 

 ance to that which forms the lithate of ammonia calculus of children. They were formed, I have no 

 doubt, in the kidney, and lay some time in its pelvis, before they were discharged. The circumstances 

 of their occurrence resemble a good deal the cases mentioned in Dr. Peout's work (p. 1 35) ; but in 

 this instance it would appear, that the production of lithic acid, and lithate of ammonia went on at, 

 or nearly at the same time ; and that adult age did not act as a bar to the formation of the latter. 

 It is exceedingly likely, however, that the augmentation of any one of those minute calculi, if detained 

 in the bladder as a nucleus, might not go on long with lithate of ammonia, except in early life. 



f Chemical Essays of Charles William Scheele, translated from the Transactions of the Royal 

 Academy of Sciences at Stockholm : Essay 9. 



MDCCCXXIX. L 



