3 I2 



STAINING AND PERMANENT MOUNTING [ CH. X 



vial of the hematoxylin solution (Figs. 243, 251 ) or one can lay 

 the slide flat on the staining rack or some other support and add the 

 stain to the sections (Fig. 248 ). It usually takes from 2 to 10 

 minutes to stain sufficiently with hematoxylin. A good plan when 

 one is learning the process is to wash off the stain after i minute 

 either with a pipette (Fig. 250 ) or by putting the slide in a dish of 

 water. Wipe off the bottom of the slide and put it under the micro- 

 scope. Light well, use a low power and one can see the nuclei 

 stained a bluish or purple color as hematoxylin is a nuclear dye. If 

 the color is faint, continue the staining until the nuclei stand out 

 boldly. Sometimes it takes a long time to stain well with hematox- 

 ylin. In such a case the jar of stain may be put into the paraffin 

 oven and the heat will accelerate the staining. One may also heat 

 the individual slides as for spreading sections, but one must be care- 

 ful not to let the stain dry on the sections. As the stain evaporates 

 add fresh stain with a pipette. 



FIG. 251. Apparatus and regents with which the slide holders are used. 

 With this^apparalus it is easy to prepare -specimens in large numbers very 

 expeditiously. After the sections are fastened to the slide and placed in the 

 holder, the slides need not be touched during all the operations until they are 

 finally ready to be mounted in balsam. Each holder contains from 12 to 14 

 slides. The bottles for the reagents are glass stoppered specimen or museum 

 bottles. (Mix, Jour. Ap. Micr. 1898, p. 777.) 



When the sections are well stained with hematoxylin, wash off 

 the hematoxylin with water. If the slide is allowed to stand some- 

 time in ordinary water the color is likely to be brighter. This is 

 due to the action of the alkali ( ammonia, etc. ) usually present in 



