Abstract
The apparatus to be described is an accurate and inexpensive hematocrit of extremely simple construction, employing heparin as an anticoagulant. Values are expressed directly in per cent by measuring the column of packed blood cells with a millimeter scale. That readings are made directly is an obvious advantage over a somewhat similar hematocrit described by Epstein, 1 with which the readings are calculated by dividing the length of the column of cells by the length of the original column of blood, and multiplying the quotient by 100.
The hematocrit here described is a pipette 12 cm. long, cut from selected glass tubing of uniform bore, having an outside diameter of 5 mm. and a bore of 0.5 to 0.8 mm. One end is beveled, and exactly 10 cm. from this end is engraved a circular mark. Before use the tube is lined with the anticoagulant by drawing an aqueous solution of 1/2 to 1% heparin through the pipette which is then allowed to dry. The tube is then sealed by encircling it with a rubber band No. 84 which is 9 cm. long and 1.3 cm. wide. No subsequent leakage occurs if this sized rubber band is placed securely around the pipette.
A rubber mouth suction tube is attached to the unbeveled end of the hematocrit, and freshly flowing blood obtained by needle prick is drawn up to the circular mark. Blood adhering to the outside is wiped away, the suction tube is carefully removed, and the pipette encircled from end to end with the rubber band. The hematocrit is now placed in a centrifuge with beveled end down and rotated for 20 minutes at 3000 r.p.m. Centrifugalization at this rate for more than 20 minutes gives constant readings.
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