Clinical diagnosis : the bacteriological, chemical, and microscopical evidence of disease / by Rudolf V. Jaksch ; tr. from the 2nd German ed. by James Cagney ; with an appendix by Wm. Stirling.

Jaksch, Rudolf v., 1855-1947.

Date:: 1890

Credit: Clinical diagnosis : the bacteriological, chemical, and microscopical evidence of disease / by Rudolf V. Jaksch ; tr. from the 2nd German ed. by James Cagney ; with an appendix by Wm. Stirling. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

39/434 (page 11)

$The cubic contents of that part of the chamber which corresponds to the field of vision can be ascertained in the following way:—The divisions of the chamber which appear in the field are first counted. Each of these measures -^ mm. across (v. supra: the area = -jj^ mm2, the cubic contents = TöVö mm3)- 11ne diameter of the field* therefore, is ^\ mm. multiplied by the number of divisions which it contains. Thus, for instance, if ten of the divisions are seen, the dia- meter of the field = iox^ mm. or |^, and the radius = |§ mm. The area of the field, therefore = ir (|£)2 mm2, and if the chamber is o. ioo mm. in depth, its cubic contents = 0.1 x (]£)2 it cubic mm. Hence we obtain the following formula : *— io x Z M x~Q where M = the number of divisions under the microscope, Z = the number of cells counted, Q = the cubic contents of the field (Q = o. i - R2, where R = the radius of the field in mm.), and where the blood is diluted in the proportion of i : io. The formula will give us the number of cells contained in a cubic millimetre of undiluted blood. When there is a very great increase in the number of leucocytes, as in leukaemia, their number can be estimated in the same manner as that of the red corpuscles, and the relative proportion of the two can be determined at the same time with sufficient accuracy, if only an adequate number of squares is taken into account. Great assistance in such experiments may be derived from the use of a 3 per cent, salt solution coloured with gentian violet, in which the leucocytes are stained, and become readily discernible from the red blood-corpuscles, which are usually somewhat paler than normal. For the same purpose, Mayet23 recommends that the blood be mixed with perosmic acid, glycerine, and water, which is said to confer upon the coloured blood-corpuscles a beautiful red tint, whilst the white corpuscles remain unaffected by it. [(b.) Gowers' Hemacytometer.t—This instrument is the most commonly used for clinical purposes in this country. The hemacytometer (fig. 6) consists of: (1.) A small pipette, which, when filled to the mark on its stem, holds exactly 995 cubic millimetres. It is furnished with an india-rubber tube and mouth-piece to facilitate filling and emptying. (2.) A capillary tube marked to contain exactly 5 cubic millimetres, with india-rubber tube for filling, &c. (3.) A small glass jar in which the dilution is made. (4.) A glass stirrer for mixing the blood and solution in the glass jar.+ (5.') A brass stage-plate, carrying a glass slip, on which is a cell * ^ = 3.1416. mm2 = square millimetre, mm3 = cubic millimetre. t Eor the above description and figure we are indebted to Landois and Stirling's Physiology, p. 19. \X In practice error is apt to arise from variation in the depth of the cell, and it is not easy to obtain one precisely A mm. Assuming that the same instrument is always used by the observer, this is best corrected by ascertaining the true depth and allowing for the error in mixing the solution. Suppose, for instance, the cell is found to have a$