2040 Journal of Applied Microscopy 



the cover-glass is somewhat outside of the zone in the direction of the cold end 

 of the plate. One-half to three-fourths of a minute suffices to fix the preparations. 



4. Heating in Thermostat. — A dry oven with thermo-regulator and thermom- 

 eter attachment gives the most uniform and satisfactory results in dry heat 

 fixation. The temperature is variously given from 110° to 135° C. It is prob- 

 able that preparations will not be spoiled within those limits, and a mean of the 

 two limits suggests itself until more definite experiments have determined the 

 optimum temperature. The time of heating is given from fifteen minutes to three 

 hours, depending upon the temperature and the method of staining to be used. 



DeCosta (1902) describes an oven for the rapid fixation of dry blood films. 

 He raises the temperature to 160° C. The gas is then turned off and the cover 

 of the oven thrown back, and after the temperature has fallen to 30° C. the 

 films are ready to stain. 



CHEMICAL FIXATIVES. 



1. Alcohol.— Hlava (1883), Malachowsky (1891), Deetjen (1901), and others 

 have used 96 per cent, of absolute alcohol for fixing dry blood films. Fixation 

 is complete in a few minutes. Goldhorn (1901) fixes fifteen seconds in pure 

 methylic alcohol. 



2. Alcohol and Ether. — Nikiforoff (1888), and subsequently many others, 

 recommend absolute alcohol and ether, equal volumes, as a fixative. Fixation 

 is complete in fifteen to thirty minutes. 



3. Alcohol followed by Formalin. — Deetjen (1901), for demonstrating the nuclei 

 of blood plates, fixed dry preparations in 98 per cent, alcohol 1 to 2 minutes, 

 dried in the air, then in 5 per cent, formalin solution 3 to 5 minutes (this solu- 

 tion should be old and have stood in the light several weeks) and washed in 

 water without drying. 



4. Chloroform. — Josne (1901) recommends chloroform for fixing blood 

 preparations. 



5. Chromic Acid. — Harris (1883) and Miiller (1889-91) used chromic acid 

 as a fixative. Miiller used \ per cent, chromic acid for ten days, and then washed 

 in running water for twelve to twenty-four hours. 



6. Flemming's Solution Lowit (1883) and Miiller (1 889-91) used Flemming's 



solution. Both first fixed with dry heat and then with Flemming's solution one 

 to six hours and washed well with running water. 



7. Formalin. — Benario ( ), Edington (1900), and Japha (1901) employed 

 formalin. Benario recommends a 1 per cent, alcoholic solution in which the dry 

 preparations are fixed one minute. Edington describes a simple apparatus for 

 fixing dry blood films with formaldehyde. A bell-jar 135 mm. in diameter and 

 150 mm. in height, having a stopper at the top, to the inner end of which is glued 

 an ordinary cover-glass, is placed over the air-dry blood preparations resting on 

 a glass plate. The stopper of the jar is removed, a drop of formalin is placed 

 on the cover-glass glued to its end, and the stopper quickly replaced in the top 

 of the jar. The cover preparation, which must be thoroughly dry, remains from 

 fifteen to thirty minutes in the formalin vapor. Japha fixed air-dried prepara- 

 tions with 1 to 2 per cent, formalin-alcohol for one minute. 



