CH. XI] 



STAINING MICROSCOPIC OBJECTS 



395 



FIG. 236. 



SMALL AQUARIUM JARS FOR STAIN- 

 ING SERIAL SECTIONS. 



ral waters. One could use distilled water, adding a few drops of a 

 saturated solution of lithium carbonate. 



Dehydrate in 95% alcohol and absolute if necessary; clear and 

 mount in balsam as described in 513. 



Hematoxylin is so nearly a pure nuclear stain for most tissues and 

 organs that the cell bodies are not very evident with this alone; hence 

 some counterstain is gen- 

 erally used also. 



640. Counterstaining 

 with eosin. One of the 

 solutions of eosin ( 562) 

 is dropped upon the sec- 

 tions after the hematoxy- 

 lin has been washed away 



with water. This stains 



R Rack for the top of the jar and contain- 

 almost instantly. One ing a small draining funnel. 



rarely needs to stain with At the left is a s P irit lam P used as a balsam 



bottle. 



eosin over 10 or 30 sec- 

 onds. The excess stain is then washed away with pipette or by dip- 

 ping the slide into water. 



641. Dehydrating and clearing. Put the slide directly into 

 95% alcohol after it is rinsed with water. Leave it in the alcohol 

 a short time and transfer to fresh 95 % alcohol or to absolute alcohol 

 a few seconds, 10-20. One must not leave the sections too long in 

 the alcohol or the eosin will dissolve out. 



Remove the slide from the alcohol and put it into a jar of clearer 

 ( 55 2 ) r P u t it on the rack (fig. 235-236) and add enough clearer to 

 cover the sections. Soon the clearer will displace the alcohol and 

 make the sections translucent. It usually requires only half a minute 

 or so. The clearer is drained off and balsam put on the sections, 

 and then a clean cover-glass is added. One soon learns to use the right 

 amount of balsam. It is better to use too much than too little ( 513). 



641a. In the past the plan for changing sections from 95 % alcohol to 

 water, for example, has been to run them down gradually, using 75, 50 and 

 35% alcohol, successively. Each percentage may vary, but the principle of 

 a gradual passing from strong alcohol to water was advocated. On the other 

 hand I have found that the safest method is to plunge the slide directly into 



