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. Pkout. 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 experiments, 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. Prout’s work (p. ] 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 
m the bladder as a nucleus, might not go on long with lithate of ammonia, except in early life. 
t Chemical Essays of Charles William Scheele, translated from the Transactions of the Royal 
Academy of Sciences at Stockholm : Essay 9. 
MDCCCXXIX. L 
