Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . e to such temperatures. Thehigher the temperature the less time is essential. Rubinstein uses a point atwhich a drop of water does not boil, but assumes the spheroidal state (so-calledLeidenfrost phenomenon) and places the slides, with the smeared side down,upon the plate at this point for one-half to three-fourths minute. Someworkers, as Pappenheim, use this point, but place the smeared side upward. Instead of the copper plate, one may use the ordinary drying oven or aVictor Meyer hea
Diagnostic methods, chemical, bacteriological and microscopical, a text-book for students and practitioners . e to such temperatures. Thehigher the temperature the less time is essential. Rubinstein uses a point atwhich a drop of water does not boil, but assumes the spheroidal state (so-calledLeidenfrost phenomenon) and places the slides, with the smeared side down,upon the plate at this point for one-half to three-fourths minute. Someworkers, as Pappenheim, use this point, but place the smeared side upward. Instead of the copper plate, one may use the ordinary drying oven or aVictor Meyer heater. It is the writers custom to use a copper drying ovenheated by a gas flame regulated by a thermostat. The slides, with the smearedside downward, are placed on a glass plate whose temperature is measuredby an accurate thermometer. The temperature is allowed to increase graduallyto about 80°, from which point it is more quickly raised until the desiredstage is approximated, when the heating must continue slowly, the final tem-perature being maintained for 15 minutes. The best temperature for Fig. 142.—Oven for fixing bloodfilms. {Da Costa.) THE BLOOD. 475 in the writers experience, is iio° to 120° for 15 minutes when the staining is tobe done with eosin-methylene blue or eosin-heraotoxylin, while for the tri-acidstain a temperature of 120° to 125° for one and one-half hours should be main-tained. Some workers heat to 160° rapidly and then allow the films to cool to 30°,when fixation is complete in about 15 minutes. Engel and Cabot recommend,in the absence of other equipment, the passing of the smear through the flameseveral times. Such treatment often yields excellent results, but is uncertainand requires much experience. It is to be remembered that too rapid changesof temperature are to be avoided, as shrinking or splitting of the cells will occurunder such conditions. So much depends upon proper fixation that a littlemore time spent in obtaining good spe
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