By this method organisms which stain by Gram's method (staphylococci, streptococci, pneumococci, etc.) are purplish-black; organisms which decolorize by Gram's method (bacilli of Friedländer, influenza bacilli, etc.) are blue; capsules are pink; nuclei of all cells are blue; and granules of eosinophilic cells are bright red. _Anilin-gentian-violet_.--Ehrlich's formula is the one generally used, but this keeps only a few weeks. Stirling's solution, which keeps much better and seems to give equal results, is as follows: gentian-violet, 5 gm.; alcohol, 10 c.c.; anilin oil, 2 c.c.; water, 88 c.c. _Gram's Iodin Solution_.--Iodin, 1 gm.; potassium iodid, 2 gm.; water, 300 c.c. _Löffler's alkaline methylene-blue_ is a very generally useful stain for bacteria. It is composed of 30 parts of a saturated alcoholic solution of methylene-blue and 100 parts of a 1:10,000 aqueous solution of caustic potash. It keeps indefinitely. * * * * * (4) Bacillus of Friedländer (Bacillus mucosus capsulatus).--In a small percentage of cases of pneumonia, this organism is found alone or in company with the pneumococcus. Its pathologic significance is uncertain. It is often present in the respiratory tract under normal conditions. Friedländer's bacilli are non-motile, {39} encapsulated rods, sometimes arranged in short chains (Fig. 10). Very short individuals in pairs closely resemble pneumococci, from which they are distinguished by the fact that they are Gram-decolorizing. [Illustration: FIG. 10.--Friedländer's bacillus in pus from pulmonary abscess (obj. one-twelfth) (Boston).] (5) Bacillus of Influenza.--This is the etiologic factor in true influenza. It is present, often in large numbers, in the nasal and bronchial secretions, and is also found in the local lesions following influenza. Chronic infection by influenza bacilli may be mistaken clinically for tuberculosis, and they should be searched for in all cases of obstinate chronic bronchitis. Their recognition depends upon the facts that they are extremely small bacilli; that most of them lie within the pus-cells; that their ends stain more deeply than their centers, sometimes giving the appearance of minute diplococci; and that they are decolorized by Gram's method of staining (Fig. 11). They are stained blue in Gabbet's method for tubercle bacilli, but are more certainly recognized by Smith's method or by Gram's method, followed by Bismarck brown or fuchsin, as follows: * * * * * Gram's Method.--(1) Make smears, dry und fix by heat. (2) Apply anilin-gentian-violet two to five minutes. (3) Wash with water. (4) Apply Gram's iodin solution one-half to two minutes. (5) Wash in alcohol until the purple color ceases to come off.