[Illustration: FIG. 57.--Extraneous matters found in urine: _a_, Flax-fibers; _b_, cotton-fibers; _c_, feathers; _d_, hairs; _e_, potato-starch; _f_, rice-starch granules; _g_, wheat-starch; _h_, air-bubbles; _i_, muscular tissue; _k_, vegetable tissue; _l_, oil-globules.] _Yeast-cells_ are smooth, colorless, highly refractive, spheric or ovoid cells. They sometimes reach the size of {131} a leukocyte, but are generally smaller (see Fig. 88, _l_). They might be mistaken by the inexperienced for red blood-corpuscles, fat-droplets, or the spheric crystals of calcium oxalate, but are distinguished by the facts that they are not of uniform size; that they tend to adhere in short chains; that small buds may often be seen adhering to the larger cells; and that they do not give the hemoglobin test, are not stained by osmic acid or Sudan but are colored brown by Lugol's solution, and are insoluble in acids and alkalis. Yeast-cells multiply rapidly in diabetic urine, and may reach the bladder and multiply there. _Mold fungi_ (Fig. 58) are characterized by refractive, jointed, or branched rods (hyphæ), often arranged in a network, and by highly refractive, spheric or ovoid spores. They are common in urine which has stood exposed to the air. [Illustration: FIG. 58.--Aspergillus from urine (Boston).] _Fibers_ of wool, cotton, linen, or silk, derived from towels, the clothing of the patient, or the dust in the air are present in almost every urine. _Fat-droplets_ are most frequently derived from unclean bottles or oiled catheters. _Starch-granules_ may reach the urine from towels, the {132} clothing, or dusting-powders. They are recognized by their concentric striations and their blue color with iodin solution. _Lycopodium granules_ (Fig. 59) may also reach the urine from dusting-powders. They might be mistaken for the ova of parasites. _Bubbles of air_ are often confusing to beginners, but are easily recognized after once being seen. _Scratches_ and _flaws_ in the glass of slide or cover are likewise a common source of confusion to beginners. [Illustration: FIG. 59.--Granules of lycopodium (Saxe).] IV. THE URINE IN DISEASE In this section the characteristics of the urine in those diseases which produce distinctive urinary changes will be briefly reviewed. 1. Renal Hyperemia.--_Active hyperemia_ is usually an early stage of acute nephritis, but may occur independently as a result of temporary irritation. The urine is generally decreased in quantity, highly colored, and strongly acid. Albumin is always present--usually in traces only, but sometimes in considerable amount for a day or two. The sediment contains a few hyaline and finely granular casts and an occasional red blood-cell. In very severe hyperemia the urine approaches that of acute nephritis. {133} [Illustration: FIG. 60.--Sediment from acute hemorrhagic nephritis: Red blood-corpuscles; leukocytes; renal cells not fattily degenerated; epithelial and blood-casts (Jakob).]