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PLATES IV, V, VI, VII.

URIC OR LITHIC ACID, C10H404N6.

Tables for the Chemical and Microscopical
Examination of Urine, § 17.

Uric acid deposits have a granular or crystalline appearance. The deposit sinks to the bottom of the vessel. It increases for some time after the Urine has been passed, is usually absent in Urine which has just left the bladder, and often is not to be detected until the lapse of several hours. It is probable that it is removed from the organism as a urate, which becomes decomposed with the separation of the insoluble uric acid.

The crystals of which uric acid deposits are almost invariably composed, vary very much in size, sometimes appearing as crystalline masses, so large as to be visible to the unaided eye (the so-called Cayenne pepper grains), sometimes so small that the deposit, by its granular character, is very liable to be mistaken for a urate, while the individual crystals are only to be detected with a quarter of an inch object-glass, and are often not more than the 1-2000th of an inch in their longest diameter.

The colour of crystals of uric acid varies much in different specimens, and we meet with every shade of tint, from a rich dark-brown colour to perfectly colourless crystals. It is rare, however, to meet with crystals of

PLATE VI.

URIC OR LITHIC ACID, C10H4N406.

Fig. 14. Uric acid crystals from Urine. These crystals were given to me by my friend and pupil Mr. Atchley.

Fig. 15. Some of the same crystals as represented in fig. 14, more highly magnified, and seen in a different position.

Fig. 16. Crystals of uric acid from Urine. Preserved in glycerine.

Fig. 17. Small uric acid crystals connected together so as to form plates.

18. Curious forms of uric acid produced by rapid crystallization after the addition of nitric or hydrochloric acid to Urine.

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