34 Dr. Venables on the Cystic Oxide, &c. 



little animal matter— principally mucus and fibrine — and a 

 small proportion of the triple phosphate. 



Chemical characters. — This urine faintly reddened litmus 

 paper; but this was clearly not the consequence of the re- 

 agency of a free acid. No decided alkaline re-agency suc- 

 ceeded, even after an interval of several days, nor did the filmy 

 deposit of the triple phosphate form on the surface *. Acetic 

 acid and spirit of wine threw down a scanty precipitate of cystic 

 oxide. Neutral carbonate of ammonia, however, threw down 

 a copious precipitate, consisting principally of the triple phos- 

 phate intermixed with the cystic oxide in greater abundance ; 

 and a filmy layer of the triple crystals speedily formed on the 

 surface of the urine. Ammonia produced nearly similar re- 

 sults, but the triple salt was more abundant, while there was. 

 no sensible portion of the cystic oxide mixed with the preci- 

 pitate. When the urine was evaporated to one-half or one- 

 third its original bulk, the acetic acid and alcohol threw down 

 the oxide in quantities sufficient to recognize its properties and 

 prove its identity. 



This urine was also very deficient in urea ; as not a particle 

 separated on the addition of nitric acid, even when evaporated 

 down to nearly the consistence of a thick syrup. Lithic acid 

 was not separable even on the addition of the concentrated 

 mineral acids to the urine evaporated to one-third its original 

 quantity. This principle, however, was not wholly deficient, 

 as was proved by evaporating to dryness, removing the phos- 

 phates, &c., and then treating the residue with nitric acid on a 

 slip of platina, heating and subsequently evaporating to dry- 

 ness. On exposing to the vapour of heated ammonia an am- 

 moniacal purpurate was formed, easily recognized by its colour. 



same re-agents before filtration. The mechanical suspension of the oxide may also 

 serve to explain the readiness with which this substance separates and concretes 

 into calculous masses in the kidneys, where the diathesis prevails ; and it supports, 

 if it do not absolutely confirm, the opinion advanced by Dr. Marcet, and confirmed 

 by all the histories hitherto detailed, that calculi of this description are exclusively 

 ^f renal origin. 



* In the two last respects this specimen differed considerably from the one 

 noticed by Dr. Prout. In the instance which occurred to him, " the mine soon was 

 covered with a greasy-looking film and at the same time speedily became alka- 

 line." But in this case the patient for a fortnight before had been taking alkaline 

 remedies, which will easily explain the tendency to become alkaline, as observed 

 by Dr. Prout. These characters, therefore, must be looked upon as arti/lcial, rather 

 than the natural and genuine result of- the "Cystic Oxide Diathesis." 



