396 STAINING MICROSCOPIC OBJECTS [Ch. XI 



water from the 95% alcohol. The diffusion currents are almost or quite 

 avoided in this way. There is no time for the alcohol and water to mix; the 

 alcohol is washed away almost instantly by the flood of water. So in de- 

 hydrating after the use of watery stains, the slide is plunged quickly into a jar 

 of gs% alcohol. The diffusion currents are avoided in the same way, for the 

 water is removed by the flood of the alcohol. This plan has been submitted 

 to the severe test of laboratory wprk, and has proved itself perfectly satis- 

 factory (1895-1908). 



§ 642. Counterstaining with the eosin in the clearer. — With this 

 method the eosin is dissolved in the carbol-xylene clearer (§ 55 2a), 

 and the hematoxylin stained sections are dehydrated with 95 % alco- 

 hol and absolute alcohol if necessary and then placed in the clearer. 

 The sections are cleared and stained in eosin at the same time. It 

 usually takes half a minute or more for the double process. When 

 the sections are clear and sufficiently red, the slide is removed and the 

 clearer drained off by holding in the forceps or in the draining funnel 

 (fi.g. 235-236). Then the balsam is added, and covered as described 

 above. 



It is a good plan to rinse off the stained clearer by pure xylene 

 before adding the balsam. This is not absolutely necessary, how- 

 ever. 



§ 643. Hematoxylin and picro-fuchsin. — Picro-fuchsin is so selec- 

 tive in its general staining that it is frequently used after hematoxyHn. 

 The hematoxyUn staining should be intense and after the hematoxylin 

 is washed away add the picro-fuchsin (§ 587). It takes only a few 

 seconds for it to act, 10 to 30 seconds. Wash with distilled water, 

 or natural water very faintly acidulated, The acid fuchsin is very 

 sensitive to alkahes and fades easily. 



Dehydrate in 95 % and absolute alcohol, clear and mount in acid 

 balsam. Acid balsam injures hematoxyhn, but is necessary for the 

 red in the picro-fuchsin. 



Look out for mercuric chlorid crystals in the sections (§ 654). 



§ 644. Hematoxylin and mucicarmine. — Tissues and organs are 

 best fixed in Zenker's or mercuric chlorid. Small intestine is one of 

 the most striking and instructive organs for this double stain. Make 

 the sections by the paraffin method, but do not fasten them to the 

 slide with collodion, for collodion stains with mucicarmine (§ 549). 



Stain I to 24 hours in mucicarmine. Wash off the stain with water 



