results; heat fixation brings out the granules well, and mercuric chloride is a good fixative for the leukocytes. The combination of fixation and staining, as in Leishman’s or Wright’s modification of the Romanowsky method, is also recommended for general work. For the _staining of blood-films_ an almost endless variety of staining-methods can be found in the literature. Many of these represent slight deviations in the method of making the stain or in its application, such deviations marking stages of improvement in the development of the method. It is not necessary, therefore, to give all of these methods, but to consider only the latest modifications of value. In a general way _blood-stains_ may be divided into five classes:— 1. =HAEMATOXYLIN AND EOSIN.= Fix in equal parts of absolute alcohol and ether for at least 30 minutes; stain with hæmalum and eosin, or Ehrlich’s acid hæmatoxylin and eosin. By adding O.5 grm. of eosin to the formula for Ehrlich’s acid hæmatoxylin a combination stain can be made that is very good for blood-films fixed by heat or absolute alcohol and ether. Stain 2-24 hours, wash, dry and mount in xylol balsam. 2. =EOSIN AND METHYLENE-BLUE.= Fix by formol (dried film over 40 per cent formol for 1 minute); absolute alcohol for 1 minute; stain 5 minutes in a 1 per cent watery eosin; then without removing eosin place in watery methylene-blue for 2 minutes; wash quickly; dry in air; balsam. 3. =MIXTURES OF EOSIN AND METHYLENE-BLUE.= The numerous mixtures of methylene-blue and eosin are not very stable, can be kept for a few days only, and give varying results. _Jenner_ improved this method of staining greatly by collecting the precipitate formed by the addition of eosin to methylene-blue, and dissolving it in pure methyl alcohol, thus giving a solution that fixes and stains at the same time. The _May-Grünwald_ method is practically the same. Jenner’s Method. a. Water-soluble eosin, 1.25 grms. Distilled water, 100 cc. b. Medicinal methylene-blue, 1 grm. Distilled water, 100 cc. Mix equal parts of _a_ and _b_ in an open basin, stirring with a glass rod. Let stand for 24 hours; filter; dry the residue at 50°C. Wash residue thoroughly with distilled water and again dry thoroughly. Take 0.5 grm. of the dried powder and dissolve in 100 cc. of pure methyl alcohol. Filter. Solution keeps well. 1. Make blood-film. Dry in air. Do not fix. 2. Cover film with stain, keeping under watch-glass to prevent evaporation Stain 2 minutes. 3. Wash in distilled water until the film has a pink color. Dry in air. Mount in xylol-balsam. Neutrophile granules are red, eosinophile rose red, basophile granules violet, red blood cells and central portion of blood-platelets are terra-cotta, leukocyte nuclei and granules in red blood cells are blue, protoplasm of nuclei and outer portion of platelets light blue.