MICRO-CHEMICAL CHARACTERS AND TESTS FOR PUS.
Pus is partly composed of a liquid portion—the liquor puris—and partly of solid cellular particles—the pus corpuscles. The liquor puris, which is merely liquor sanguinis, contains a variable amount of albuminous constituents, and urine, therefore, which contains pus must also show evidence of albumin iu proportion to the amount of pus present. It is often a matter of considerable difficulty to decide as to whether the amount of albumin present can be accounted for by the pus, or whether there is albumin from renal degeneration super added. This, however, will be treated of under the head of acciden tal albuminuria.
The pus cell microscopically is spherical and larger than a blood corpuscle, having a diameter of to millimeter, and is heavier. Sometimes it is irregular in shape from the processes it sends out. * Spherical forms mark transitory pyurias. If water is added the cell becomes larger as well as clearer. If acetic acid is added the nucleus will be seen divided into three or more nucleoli. Similar
changes occur in the urine. If the secretion he acid and concentrated the pus cells appear small and granular, if the urine be alkaline or of low specific gravity the pus cells are large and swollen. The chemi cal test for pus in the urine is identical with one of its chief clinical characteristics. If liquor potassce or liquor ammonim be_ added to puriform urine, the pus becomes converted into a viscid mass (Donne's test). Puriform urine is always more or less murky. In acid or neutral urine the pus sinks to the bottom of the glass and forms a more or less thick creamy layer. But in urine alkaline from ammoni acal decomposition, the pus is transformed into a clear viscid, glairy, tenacious mass. To distinguish between pus and mucus t when both are present is often difficult : it is advised to acid mercuric chloride, which precipitates the pyin but not the muciu; this is filtered off and the filtrate containing the mucin is precipitated by acetic acid.