( ii. XI] 



STAINING MICROSCOPIC OBJICCTS 



395 



Fig. 236. 



Small Aquarium Jars for Stain- 

 ing Serial Sections. 



R Rack for the top of the jar and contain- 

 ing a small draining funnel. 



At the left is a spirit lamp used as a balsam 

 bottle. 



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

 saturated solution of lithium carbonatr. 



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 

 almost instantly. One 

 rarely needs to stain with 

 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 

 (§ 552) or put 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 05'; 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 safesl method is to plunge the slide directly into 



