The following technic is of the greatest value not only because it makes the red cells more distinct but because by staining the various epithelial elements it gives us more exact information as to distinction between the segmented nucleus of pus cells and the single one of renal cells. Make a streak of vaseline across a slide one inch from one end. Then deposit a drop of urinary sediment, taken up from the centrifuge tube with a pipette, about ¼ inch from the grease line. Then drop a large drop of Gram’s iodine solution on this sediment and then apply one side of a square cover-glass to the vaseline line and allow it to fall gently on the drop of sediment and stain. There is no current motion, and casts and other urinary elements remain under the cover-glass instead of floating out beyond the margins. It is well to examine the unstained sediment with a ⅔ inch objective before adding the iodine and applying the cover-glass, as one gets a better idea of casts with a low power and unstained than in any other way.
With haemoglobinuria we necessarily turn to chemical or spectroscopic tests which are also applicable to microscopically doubtful cases of haematuria.
For the detection of occult blood, the technique described on [page 524] should be observed, and alkaline urines faintly acidified with acetic acid before examination.
Indicanuria.—In sprue and pellagra we have a rather marked increase in indican. It is probable that many cases of vague manifestations of neurasthenia with loss of physical and mental energy are connected with auto-intoxication rather than tropical heat or intestinal parasites.
Urobilinuria.—In conditions where there is a great destruction of red cells tests for urobilin are important. Plehn considers the presence of urobilin as of importance in the diagnosis of latent malaria, which is true, provided other causes for red blood cell destruction are excluded. Blackwater fever cases usually show an intense urobilinuria. Urobilinuria is also a sign of deficient functioning of the liver.
Bile Pigment Tests.—In conditions associated with the presence of bile pigments in the urine we may conveniently employ the Gmelin test in the following manner. Filter the urine several times through the filter and then touch the moist inner surface of the paper with a glass rod dipped in commercial nitric acid. A ring-like play of colors, green, blue, violet and red circle out from the spot touched. A green color must be noted for positive diagnosis.
Tests for bile acids seem to have but slight value in differential diagnosis.
A very simple and apparently quite reliable test for deficiencies in liver functioning is that known as Ehrlich’s aldehyde reaction. The reagent is a 2% solution of p. dimethylaminobenzaldehyde in equal parts of water and concentrated hydrochloric acid.
For the test treat 5 cc. urine with 5 to 10 drops of the reagent. Agitate a few minutes and a positive reaction is shown by a fine cherry-red color, thought to be due to urobilinogen.