312 THE MICROSCOPIST. 



with which it is associated. In Bright 's disease these 

 casts, in addition to albuminous urine, assume consider- 

 able clinical importance. In the acute form of the disease 

 the cylinders or casts are fibrinous, with blood, mucus, 

 or pus cells, and epithelium. Towards the close the casts 

 become homogeneous or hyaline. In chronic desquama- 

 tive nephritis the cylinders are without blood, arid to- 

 wards the end waxy or fatty, often containing many oil- 

 globules (Plate XXVI, Fig. 241). The specimen of urine 

 examined for casts should have settled for several hours, and 

 the drop of sediment examined should be carefully focussed 

 and illuminated. The casts are of various sizes, those of 

 very large diameter indicating dilation of the renal tubules. 

 In bloody or purulent urine tube-casts point out a renal 

 element in the case. They do not always indicate Bright's 

 disease, as they may be associated with the irritation of 

 a calculus, and are sometimes found in jaundice without 

 serious renal trouble or albuminuria. 



CRYSTALLINE AND AMORPHOUS DEPOSITS. 



Uric Add. Crystals of uric acid may often be recog- 

 nized as a red sand, lying at the bottom or on the sides 

 of the vessel, or entangled in mucus. They may be yel- 

 low, red, or brown, from coloration by urinary pigment. 

 Their microscopic forms are various, but are usually some 

 modification of the rhomb. Thus they may be rhomboid 

 tablets with obtuse angles, or the shape of a whetstone 

 (Plate XXVI, Fig. 242). When slowly precipitated, uric 

 acid may form druses of four-sided prisms (Plate XXVI, 

 Fig. 243). When precipitated from fresh urine by the 

 addition of muriatic acid, the crystals are large and often 

 of various shapes. They may be tested by dissolving in 

 potassa and reprecipitating by muriatic acid, when they 

 assume the shape of Fig. 244, Plate XXVI. Crystals of 

 uric acid may occur as a film as well as a deposit. They 

 originate from tissue-waste, excess of nitrogenous food, 



