A MICROHEMATOCRIT METHOD AND ITS EVALUATION

Iii experiments with small animals and hematologic examination of children, the need often exists for a hematocrit method requiring amounts of blood much smaller than those needed for the usual AVintrobe tube. The procedure described here requires minute amounts of blood such as may be obtained from the fingertip, heel, ear or tail. AVhile the necessary apparatus (a heavy-walled capillary pipet sealed with a thermolabile plastic material) entails no novel idea, a description of the technic and its evaluation as compared with the AVintrobe tube is deemed worthy of note. A large literature exists on microhematocrit methods, but comparison of results with those obtained with the established AVintrobe tube is insufficient. Microhematocrit apparatus with a fine capillary tube and with a permanent seal at one end, in the manner of the AVintrobe tube, avoids leakage but poses the problem of easy placement of the blood into the small bore. Some workers have attempted to meet this problem by employing a special tube with a cup at the open end -; this type of tube is expensive and difficult to clean. Capillary tubing open at both ends overcomes these drawbacks but presents the problem of adequate sealing of one end after the sample is drawn up. Solutions to this problem have included metal clips, rubber bands with a reinforcement of tire patch material or wax, and a plastic material.