Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . advisable to THE BLOOD. 421 point the instrument at some dark object and to avoid direct sunlight, as theshadings of color are not so easily matched by direct daylight. As soon asthe colors are matched make the readings and check the results with severalduplicates. This reading is observed on the left side of the. case in the smallopen space, the line which coincides with the beveled edge of the openingrepresenting the percentage of hemoglobin, on the basis of a value of of
Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . advisable to THE BLOOD. 421 point the instrument at some dark object and to avoid direct sunlight, as theshadings of color are not so easily matched by direct daylight. As soon asthe colors are matched make the readings and check the results with severalduplicates. This reading is observed on the left side of the. case in the smallopen space, the line which coincides with the beveled edge of the openingrepresenting the percentage of hemoglobin, on the basis of a value of of hemoglobin per 100 as 100 per cent. It is, therefore, easy tocalculate the direct amount of hemoglobin in the blood examined. This instrument has the advantages that undiluted blood is used, that thescale of comparison is usually very accurately standardized, that it is con-venient, easy of manipulation, and rapid in giving results. Coagulation ofthe blood does not occur sufficiently soon to introduce an error, providing thereading is taken within a reasonable time. It is more convenient for general. Fig. 127.—Method of filling the Dare blood pipet. {Da Costa.) use than is the Miescher, is less expensive, can be used in a light room, andgives results second only to those of the Miescher. The disadvantages of thisinstrument are that an occasional faulty standardization may introduce errors,it costs much more than some of the instruments to be described, and it isnot a long-lived instrument unless care is taken in handling it. In the writerslaboratory this instrument has given great satisfaction and can be recommendedfor general use on the ground of its convenience and ready application to clinicalwork. Hemometer of Sahli. This instrument is a new modification of the older hemoglobinometerof Gowers, and has so many advantages over the older instrument that thislatter will be passed over. A modification of the Gowers instrument intro-duced by Haldane is simple and reliable,
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