150 HISTOLOGY OF THE TEETH. 



and eosin, which is by far the best double-stain for general 

 use, add lo drops of hcematoxyUn to a watch-glass of dis- 

 tilled water, place the sections in it, and let them remain one 

 or two minutes or until they assume a light straw colour. Tho- 

 roughly wash in ordinary water and place in the eosin stain. 

 Dehydration and eosin-staining can both be accomplished at the 

 same time ; a matter of great importance, if you intend to mount 

 in balsam. To do this keep on hand a saturated solution of 

 eosin in absolute alcohol. When a stain is wanted, add a few 

 drops of this solution to a watch-glass of ordinary alcohol. 

 Having stained the tissues, rinse in absolute alcohol, and place on 

 the slide ; with a camel's-hair brush or pipette, drop several drops 

 of oil of cloves on the section. Set aside and allow to clear, 

 which will require several minutes. Examine, from time to time, 

 under the microscope without placing the cover-glass, taking care 

 not to let the objective touch the oil. When sufficiently clear, 

 remove the surplus oil of cloves, and drop on the section sufficient 

 balsam, thinned with chloroform, to cover the section ; then 

 place the cover-glass and put aside for the balsam to harden. 



For the double staining, place several sections in a h per cent, 

 solution of picro-carmine,made after the following formula (Frey) :— 

 Carmine i gramme (about 15 grs.), liquor-ammonia 4 c.cm., 

 aqua, 200 grammes. Mix and add 5 grammes picric-acid; shake 

 thoroughly. After settling, draw off so as to leave the undissolved 

 picric-acid behind. Evaporate in a shallow dish in the open air. 

 A red powder is thus obtained, with which J per cent, solution with 

 distilled water is to be made, and allowed to stand several days, 

 when it can be filtered, and is ready for use. Sections should be 

 allowed to remain in this solution at least twenty minutes. A 

 longer time does not matter. When sufficiently stained, remove to 

 a watch-glass of distilled water, which had previously been acidu- 

 lated by adding a few drops of acetic acid ; this brings out the 

 colour and fixes it. 



To double-stain these sections with haematoxylin, place in 

 dilute hsematoxylin for a few minutes ; wash in water, dehydrate 

 in alcohol, place on side, clear with oil of cloves, and mount 

 in balsam. To double-stain with methyl-green, take the sec- 

 tions previously stained in picro-carmine, and place them in 



