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.
44/570 page 40
![Many close observers find that their pipettes vary with the tem- perature. While accurate information on this point is not at hand it is just as well to avoid extremes of temperature in making the tests and in cleaning the instrument. It has been suggested that the polycythemia of high altitudes is partly referable to variations in the hematocytometer due to changes in atmospheric pressure, but this suspicion has not been confirmed. The condition of the pipette is of prime importance. Absolute ' dryness of the tube and bulb is essential. The collection of minute water drops in the tube and bulb is responsible for many of the shadow corpuscles sometimes seen in the counting-chamber. Every few weeks a pipette should be cleaned out with concentrated nitric acid. (/) Cleaning the Apparatus. After using the pipette the rubber tube may be transferred to the long arm and the remaining fluid expelled. The tube should then be cleaned thoroughly with water, then with alcohol and ether, or, better, with pure ether. It must be thoroughly dried before using again. The counting-chamber must be cleaned with water only, as alcohol and ether dissolve the cement under the shelf and plate. (g) The Limit of Error with the Hematocytometer. Lyon, Thoma (and Reinert), counting an average of 1141 cells in 100 squares with a dilution of 1 : 200, found an average error of 1.82 per cent, in 24 preparations of the same specimen, and in another case, counting an average of 934 cells in 100 squares, 1 : 200 dilution, an average variation of 2.71 per cent., in 12 preparations of the same specimen (Limbeck). These results in the hands of experts using special care indicate that a variation of 150,000 cells (3 per cent.) cannot be accepted as of any significance. More accurate data are, however, seldom required by the clinician. Oliver's Hematocytometer. The Principle. When a candle flame is viewed through a flat glass tube containing water a trans- verse line of bright light is seen which results from the blending of numerous images of the flame. The images are produced by the minute longitudinal corrugations in the glass which reflect the light in various directions. When diluted blood is placed in the tube the fluid is sufficiently opaque to shut out the images until a certain dilution is reached, when a bright streak of light becomes rather suddenly visible. Oliver believes that the appearance of this bright horizontal line is a very sensitive indicator of the proportion of red cells in the fluid, and by a long series of observations has devised an instru- ment for determining the number of red cells in blood according to this principle. The apparatus consists of a measuring pipette (A); a dro])- per for Hayem's fluid (B); a flat glass tube graduated in 120 degrees (C). The Procedure, The capillary pipette is carefully filled with blood and washed into the tube by means of Hayem's fluid. A proper amount of fluid is then added to the diluted blood, and](https://iiif.wellcomecollection.org/image/b21503886_0044.jp2/full/800%2C/0/default.jpg)
