The blood, how to examine and diagnose its diseases.

  • Coles, Alfred Charles.
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: The blood, how to examine and diagnose its diseases. 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.

    30/318 (page 14)
    tube the blood and water are thoroughly mixed, and then water added till the compartment is quite full. The other side is filled with water only, so that on one side we have a mixture of water and blood and on the other water alone. The cylinder is then placed on the circular opening of the stage, so that the coloured part is directed away from the finger screw, whilst the side containing the water is over the wedge of coloured glass. Artificial light, such as that afforded by a lamp or gas (daylight, electric, or incandescent light cannot be used), is reflected upwards from the plaster of Paris reflector, and it is generally better to use as little light as possible. The coloured glass is then moved along, preferably in jerks, and not too gradually, till the red tint in both compartments appears equal and the percentage noted. Daylight must be excluded as much as possible, and it is easier to estimate the intensity of the two colours when the axis of the eyes is at right angles to the septum, which divides the cylinder into two equal compartments, the lateral portions of the retina beino- more sensitive to colour impressions. One eye only'^should be used, and that at the ordinary reading distance from the stage. Sometimes a piece of paper rolled into a tube may be looked through, as this, by cutting off any light in the room, renders a sharper definition possible. The whole process only occupies one or two minutes, and the results are very fairly accurate. It renders the greatest assistance in watching the progress of cases^ especially chlorosis, and sometimes obviates the necessity of a long count of the red corpuscles.