BACTERIA. Normal urine in the normal blad der contains no bacteria. Non-pathogenic bac teria are, however, frequently added to the urine from the urethra or from the external genitals. Of these the Microcoecus urea> is one of the most common. The smegma bacillus is also sometimes present in large numbers and is important from the similarity which it bears to the tubercle bacillus as regards its staining qualities. Of pathogenic bacteria found in urinary sediments may be mentioned the Staphylococcus pyogenes, Streptococcus pyogenes, the colon bacillus, tu bercle bacillus, and gonococcus. In such infec tious diseases as septieremia, ppemia, erysipelas, diphtheria, and tuberculosis the specific germ of the disease is sometimes found in the urine. For descriptions of the appearance which these dif ferent germs present under the microscope the reader is referred to the special articles on the diseases which they cause. For a description of the staphylococcus and streptococcus the reader is referred to the article on BACTERIA. fn ex amining urinary sediment for bacteria, a small amount of the sediment is taken up with a plati num loop and smeared on a cover glass in a thin layer. This is allowed to dry. To fix the spec•imnen on the cover glass, the cover glass is passed through a blue flame of sufficient heat to bring the specimen just to the boiling point of water. The specimen may now be stained by
placing upon it a few drops of a watery solution fuehsim gentian violet, or methylene blue. After staining it is washed in water and may then be examined.
For other organisms more rarely present in urine the reader is referred to special works upon microscopical urinalysis.
Iltoon. The main purposes for which blood is examined microscopically are as follows: (1) To determine the number of red blood cells.
(2) To determine the richness of the red cells in leemoglobin.
(3) To determine the size, shape, etc., of the red cells and the presence of forms of cells not found in normal blood, e.g. nucleated red blood cel Is.
(4) To determine the number of white blood cells.
(5) To determine the relative proportion of the different kinds of white blood eells=differen tial count of leucoeytes.' (0) For the plasmodium inalarice.
(;) In suspected typhoid for Widal's reaction. (8) For bacteria and other foreign substances. For description of the normal histology of blood the reader is referred to the article on