acid, acid alcohol, acid stains, aniline oil, aniline-xylol and alcohol. Some workers use the regressive method for such simple stains as hæmatoxylin, overstaining, and then differentiating with acid alcohol before counterstaining with eosin. The results obtained in this way are much less satisfactory than is possible with the progressive method. Tissues may be stained in the body during life (_intravital staining_), or immediately after removal from the body (_supravital or survival staining_), either before or after sectioning. (See Page 217.) Fixed tissues may be stained in bulk or in sections. Staining Tissues in Bulk. This method is not often used in pathologic work. The fixed and hardened tissue is cut into small pieces, placed in the staining solution for several days, washed thoroughly, dehydrated in alcohol, imbedded, cut, and mounted without further staining. Alcoholic solutions penetrate best; hæmatoxylin, hæmalum, carmine and alcoholic solutions of the aniline stains may be used. _Metallic impregnation_ (gold or silver salts) of fresh or fixed tissues is but little used in pathology. (See Staining of Nervous System, and Spirochætes.) Staining of Sections. =Celloidin sections= are lifted from water or alcohol into the stain by the needle or section-lifter. The use of the latter is advised, as by it the section can be floated flat on to the staining solution. When many celloidin sections are to be stained at once they can be stained in small tea-strainers and transferred in these from one solution to another. =Paraffin sections= may be floated directly on to the stain without removing the paraffin; or they may be stained on the slide or cover-glass after removing the paraffin, the stain being dropped on to the section, or the slide or cover-slip is immersed in the stain. Special staining-dishes for the staining of paraffin sections on slides and covers can be obtained. Paraffin sections transferred to celloidin sheets by the plate method can be put into the staining-solution while on the glass-plate, or the films can be detached and transferred from one solution to another by means of forceps. This is the easier way, and it is not necessary to touch the films with the fingers. General Rules for Staining. 1. The stain should be filtered just before being used, in order to remove precipitates, moulds, etc. Unless they have been diluted most of them can be used over and over again, hence after using they should be filtered back into the stock bottle.