1903] KELLOGG: — STUDIES FOR STUDENTS 121 



covered (leaving always i sq. in. at one end for the label, to be put on later) gently 

 flow enough distilled water from a pipette over it to float up all of the sections. 

 Put the slide in a safe place to allow the water gradually to evaporate and the sec- 

 tions to dry thoroughly : they will, presumably, have spread out and dried perfectly 

 flat and unfolded against the thinly smeared surface of the slide. Now gently heat 

 the slide over a small flame until the paraffine of the sections has melted and thus 

 further flattened and settled the sections against the glass surface. Let the paraf- 

 fine harden, and put the slide into a small glass jar of pure xylol. 



Clearings stai?ivig, and mounting. — The xylol will dissolve away the parafflne in 

 and enclosing the sections ; leave slide in xylol for at least fifteen minutes ; even 

 a longer time is better. Then transfer to absolute alcohol for fifteen minutes to 

 remove the xylol; then to 95% alcohol for from five to ten minutes; then to 75% 

 alcohol for five minutes; then to 5o'}{, alcohol for five minutes ; then into the alco- 

 holic staining solution. There is a host of stains, some simple, some complex, some 

 for general use, some for very particular and limited use. The beginner wants a 

 simple stain for general use ; and if he can get it in alcoholic solution, acidulated, 

 he is relieved from carrying his slide through three or four more little jars contain- 

 ing, variously, water and acidulated alcohol. Transferring the slides through the 

 alcohol series of lessening strength is simply to prevent the dangerously violent 

 diffusion currents which are set up when an object saturated in strong alcohol is 

 brought directly into weak alcohol. And if a stain in aqueous solution is used the 

 series has obviously to be a longer one. For the beginner I recommend the use of 

 Ehrlich's acid haematoxylin as a thoroughly satisfactory general stain. It is strong, 

 staining quickly ; it is an alcoholic solution, saving running the slides down to 

 water; it is acidulated saving the differentiating bath in acid alcohol. It is cheap, 

 and is a sharp, clean, pleasantly colored stain. 



Leave slide in this stain from two to five minutes ; only experience will deter- 

 mine the actual time for each slide. Wash slide in 50% alcohol; transfer to 75% 

 alcohol for ten minutes; then to 85% alcohol for five minutes; then to 95% alcohol 

 for five minutes ; then to absolute alcohol for ten minutes ; then to xylol for ten 

 minutes. With thin balsam ready, remove the slide from xylol and put three or 

 four drops of the balsam on it, and carefully but quickly, so as to prevent drying 

 of any part of the slide by evaporation of the xylol, put the long cover-glass on in 

 such way as to drive out all air-bubbles. Keep slide gently heated in paraffine 

 oven or on top of imbedding triangle for half a day so as to harden the balsam ; 

 label and tuck away. 



Keep the xylol, alcohol, and stain in little cylindrical staining jars or shell 

 vials 3^ in. high by i^ or 2 in. in diameter with class tops ground on, or good 

 corks. Have a double series of alcohol jars, one set for the slide in its passage 



