The signs of internal disease, with a brief consideration of the principal symptoms thereof . tingthe blood corpuscles is the cytometer of Thoma-Zeiss, manufacturedby Zeiss. It consists of a diluting pipette for the red corpuscles,another for the white, a specially ground cover-glass and a counting ?242 EXAMINATION OF THE BLOOD chamber in the bottom of which is placed a disc ^ ruled into squareswhose sides measure 1-20 mm. and whose areas are therefore 1-400of a square millimetre. The depth of the chamber when the cover-glass is in position is 1-10 mm. When the chamber is filled the con-tents
The signs of internal disease, with a brief consideration of the principal symptoms thereof . tingthe blood corpuscles is the cytometer of Thoma-Zeiss, manufacturedby Zeiss. It consists of a diluting pipette for the red corpuscles,another for the white, a specially ground cover-glass and a counting ?242 EXAMINATION OF THE BLOOD chamber in the bottom of which is placed a disc ^ ruled into squareswhose sides measure 1-20 mm. and whose areas are therefore 1-400of a square millimetre. The depth of the chamber when the cover-glass is in position is 1-10 mm. When the chamber is filled the con-tents overlying each square will be a column 1-400 ^^- ^ase by 1-10mm. in height or 1-4000 cu. mm. Hence the number of corpuscles overlying one square X by4,000 would equal the number of corpuscles in a. cubic millimetre ofblood, if the blood examined were undiluted. Since it is impossible tomake the count without diluting the blood to 100 or 200 times its ownvolume, the above product must be multiplied by the dilution mul-tiple. Furthermore, since great variations occur in the number of. Fig. 62—Thoma-Zeiss Hemacytometer Pipette, and Chamber. corpuscles found in the various squares, in practice it is actuallynecessary to count the corpuscles overlying a largQ number of squares,divide by the number of squares counted in order to obtain an average,then multiply by the other factors. By reason of the ruling presentlyto be described, it is found convenient to count a field 16X16 or 256squares. Suppose the number therein totals 1,792, giving an averageof 7 for each square, the dilution being 200. Then 7X4000X200=5,600,000 cells per cu. mm. of blood. Countimg; chambers with therulings of Turck enable the enumeration of both red and white cells,to be made in the same specimen. In this apparatus the small 1-20mm. squares are fenced off into blocks of 4X4 or 16 of the smallersquares, separated by interspaces or alleys, the width of the smallsquares. For enumerating the red discs, the
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectdiagnos, bookyear1906
