Clinical pathology of the blood : a treatise on the general principles and special applications of hematology / by James Ewing.
- Ewing, James
- Date:
- 1904
Licence: In copyright
Credit: Clinical pathology of the blood : a treatise on the general principles and special applications of hematology / by James Ewing. Source: Wellcome Collection.
Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.
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![Two cells are provided, one with a depth of 15 mm the other with a depth of 12 mm., the percentage of Hb benig obtauied with the deeper cell, and the other being ased as a control specimen and ffivins: only 4 iU) of the actual percentage of Hb. T\Lece\ih]v.re a projeeiing partition dividing the compartments along which a grooved cover-glass (D) may be slid, without fear of mixL the blood and water. If an excess of the blood solution overflows the side of the cell during the adjustment of the cover, no harm results, as the blood is already properly diluted in the pipette, and the depth in the chamber will always be 15 mm. (or 12). Ihese chancres add very much to the facility and precision of the method. Finally, the cells are covered with diaphragms transmitting a ray of liffht 'which includes only three degrees on the scale, thus giving practically a single color of the wedge for comparison with the blood. In the procedure the blood is diluted in the pipette as with the heraatocytometer, the diluting fluid being distilled water or a filtered 1 per cent, solution of sodium carbonate. After shaking and clear- ino- the tube of diluent, one chamber in each cell is filled with dihitecl blSod, the opposite chamber with distilled water, and coyer-glasses and diaphragms are adjusted. Using a small candle and shielding the eyes from light, the readings with tjie two cells are carefully taken The reading with the small cell should be f that with the larger. If there is any variation one reading may be used to correct the other. For example, suppose the readings to be : For the larger chamber (15 mm.) ^ For the smaller chamber (12 mm.) If the first reading were absolutely correct the second reading should have been 51.2, since 64X^ = 51.2. Or, assuming the second to be correct, the first should have been 62 5, since QOxi = 62.5. The mean of 64 and 62.5, i. e., 63.25, should be taken as the true value. . If the original dilution was 1:200, the percentage of Hb is 63.25, the corrected result with the larger cell, but if the c liution has been 1 : 300, this result must be multiplied by U, or it 1 : 400, ^^Tlie technical difficulties of this method are so slight and the results so accurate that the instrument may be recommended over any other yet devised for this purpose. _ 4 Oliver's Hemoglobinometer. This instrument is constructed on the excellent principle of the tintometer, which is extensively used in various arts and industries. It consists of a series of six red glass disks (a) mounted upon white plaster mirrors in convenient frames. These disks represent the colors of twelve solutions of blood containing twelve chfferent proportions of Hb. Two sets of disks are made, one for reading in daylight, the other for candlelight. The latter give more accurate results and should be chosen. The intermediate percentages of Hb are secured by means of riders of colored glass to be placed over the disks, and which represent respectively 2i and 5 per cent, ot Mb](https://iiif.wellcomecollection.org/image/b21503886_0052.jp2/full/800%2C/0/default.jpg)
