78 THE AMERICAN MONTHLY. [Mnrdi, 



the thin cover. \Vc then replace the picro-carmine by a preserva- 

 tive liquiil. with precautions t(» be referred to hereat"ter. Tissues 

 tixetl bv t>smic aci«l or by the bichromates are staiueil by picro-car- 

 mine with jjreat (htlicnlty .... Sucli sections are placed for 24 

 hours in a c«>rketl tube tilled with a mixture of etpial parts of picro- 

 carmine and water. They are then washed, and mounted as 

 described for sections treateil with alcohol. This does not jjive 

 the fine results obtained by the precedin<j method. The wash- 

 ings fieeded to remove the picric acid destroy those shades of 

 color obtained by tlie action of picro-carmine .... 



Alum carmine. — . . . . Ammonia alum, i to 5 jjrms. ; car- 

 mine. 4 grms. : distilled water, 100 grms. Boil for 20 minutes, 

 takinj; care to maintain the ori<;inal volume by addinjj water. 

 Filter aiul preserve by a crystal of thymol. It is a nuclear stain 

 of the first order: it colors admirably the nuclei of tissues fi.xed 

 bv osmic acid, which makes it valualile in many cases where 

 jiicro-carmine is worthless. And. turther, the color is well 

 preserved in glycerin. Place the sections for a few hours in a 

 vessel containing one c. c. of alum carmine, and wash until the 

 excess of color has been removed. 



This stain is exceedingly penetrating, so that tissues may be 

 colored '• in mass." After washing, which follows the action 

 of the fixative, place the specimen in a test-tube containing 2 or 

 3 c. c. of alum carmine. After a variable time (one or two 

 (lavs) transfer to water, which should be renewed as long as it is 

 tinged with carmine. The tissue is then passed through alcohol 

 and imbedding materials. . . . 



Haematoxylin. — . . . . With a little attention it is here 

 possilile to get good coloring after all fixing reagents, but to 

 obtain perfect nuclear selection the haematoxylin should be 

 applietl to pieces fixed by the bichromates. The best way to 

 use it is to put the sections in a vessel w ith a few drops of the 

 stain. If the tissue has not been long in the biciiromate, it will 

 stain in from i ^ to 20 minutes ; with other re.igents, one or two 

 hours are needed. When stained, wash in water and mount 

 in balsam : glycerin destroys the color. Beautiful preparations 

 may be had by combining haematoxylin and eosine. 



Aniline colors. — . . . . Of these, procure methyl green, 

 eosine. tjuinolein blue, safranine. gentian violet, and methyl 

 blue. The best wav to use them is to make saturated solutions 

 in absolute alcohol, and keep in well-stoppered bottles. They 

 should be filtered when needed, and diluted with an equal 

 volume of distilled water. . . . Eosine is habitually used as a 

 complement to Ranvier's hapmatoxylin, by placing the section 

 stained bv ha-matoxvlin on the slide, washing it well, and 

 coloring with eosine in alcc>hol or in water. . . . 



Impregnations. — This name is given to the coloring pro- 

 duced l)v the formation within the elements of metallic deposits 

 in a state of very fine subdivision. Nitrate of silver and chloride 

 of gold are always used for this purpose. 



