40 THE MICROSCOPE. 



with separate ossification of the lens, also seems to be pecu- 

 liar. 



There can be no doubt as to the genuineness of the bone 

 in this case. Both pieces showed lacunae and canaliculi very clearly, 

 and the plate showed Haversian canals, with a somewhat con- 

 centric arrangement of lamella; as well. The specimen is in 

 the possession of Prof. Froth ingham. 



URIC ACID. 



BY C. H. STOWELL, 



URIC acid is deposited as a sediment only when the urine has 

 an acid reaction. The sediment is never colorless, although 

 it may have but a pale-yellow color. It has, usually, either a 

 deep yellow, an orange, or a brown color. The unaided 

 eye is generally sufficient to identify the presence of uric 

 acid, for it is the only substance giving a spontaneous deposit 

 of brown crystals. The crystals usually lie scattered as colored 

 specks on the sides of the glass vessel, forming also a layer 

 of deposit at the bottom. It appears in many different forms 

 under the microscope, the more common being that of smooth 

 tables of the rhombic form. These rhombic crystals are mod- 

 ified by having their angles rounded off in such a way that 

 spindle-shaped crystals are produced. Other varieties exist, as 

 dumb-bells, six-sided plates, rectangular tables, saw-shaped, fan- 

 shaped, etc. If there be any doubt as to the nature of any 

 particular form it is only necessary to dissolve the sediment 

 on the glass-slide in a drop of potassic hydrate, and then add 

 a drop of hydrochloric acid, when the usual form will appear. 

 Uric acid is insoluble in hot water but soluble in alkalies, 

 potash, soda and ammonia. Some of the sediment, supposed 

 to be uric acid, may be placed on a slide and a drop of 

 .strong nitric acid added to it. After evaporating it to dry- 

 ness, one or two drops of ammonia are added. If a purple- 

 violet or vi(jlet-red color appears it denotes the presence of 

 uric acid or a urate. In testing for an excess or for a de- 

 ficiency of urea the quantity of urine passed in twenty-four 

 hours should be taken into account. If the amount passed be 



