in the Museum of St, Bartholomew's Hospital, 4-19 



ammonia containing a little oxalate of lime, around this is 

 oxalate of lime nearly pure, a white layer three eighths of an 

 inch in thickness follows, and is followed by a thin stratum of 

 oxalate of lime of a very dark colour; upon this is deposited 

 crystalline uric acid marked with the irregular concentric 

 lines peculiar to oxalate of lime calculi, although it contains 

 but a mere trace of that substance : the whole was coated by 

 urate of ammonia, uric acid, and oxalate of lime irregularly 

 deposited. As in the museum catalogue the white layer was 

 merely described as fusible, and as Dr. Prout (to whom, 

 with the permission of Mr. Stanley, I had the pleasure of 

 showing this specimen,) suggested that it might contain urate 

 of soda, it was carefully examined for that substance, and the 

 result was, that in addition to the mixed phosphates with 

 some carbonate of lime, a small quantity of uric acid and soda 

 was present. The quantity of the latter was, however, very 

 minute; oxalate of lime could not be detected. 



It is highly probable that in this case the deposition of the 

 phosphates had been caused by the use of alkaline remedies, 

 and that on the discontinuance of these, the former diathesis 

 had returned. If this were the case it can hardly be consi- 

 dered as a fair exception to the law above mentioned. 



By most writers on this subject, a species of calculus has 

 been noticed, consisting of the different ingredients mixed in- 

 discriminately together, from which circumstance it has been 

 termed mixed or compound. The only specimens which ap- 

 pear to me to deserve this appellation are the mixed phos- 

 phates and the less pure varieties of urate of ammonia. As 

 however there is no calculus which is absolutely pure, and it 

 would be exceedingly difficult to decide what proportion of 

 the dissimilar ingredients should constitute a mixed calculus, 

 this class has not been included in the arrangement. I may, 

 however, remark that with the exception of those layers which 

 occasionally intervene between two different deposits, and 

 which, as has been remarked by Dr. Prout, usually consist of 

 a mixture of the old and new layers, only two specimens have 

 come under my notice at all approximating to the so-called 

 mixed calculus, or in which the slightest hesitation occurred in 

 assigning their proper place : of one of these I have given the 

 analysis under the head of urate of ammonia: the other con- 

 tained a much larger relative proportion of the mixed phos- 

 phates and surrounded a nucleus of uric acid, it was therefore 

 arranged among the alternating calculi. Although in the 

 foregoing observations I have endeavoured to conhne myself 

 to points of general interest or on which a difference of 

 opinion existed, yet I am afraid they have already extended 

 to too great a length, and 1 shall therefore no longer intrude 



2 C) 2 



