110 A MANUAL OF BACTERIOLOGY 



and filtered through muslin, and to every 100 c.c. of the 

 mixture 1 grm. of sodium salicylate is added. The slide 

 is smeared thinly with this, the section is transferred to 

 it and afterwards dried in the manner above described. 



Supposing that the sections, in spite of all precautions, 

 curl up as they are cut, it is still often possible to obtain 

 a few that can be mounted. They may sometimes be 

 unrolled by cautious manipulation with a couple of 

 needles after having been softened by warming, or a needle 

 or knife-blade may be held close to the edge of the micro- 

 tome knife during cutting, so that curling is prevented. 



Tissues embedded in paraffin may be kept indefinitely in 

 labelled pill-boxes and cut all at once or from time to time as 

 required, or the ribbons of sections may be preserved in a box 

 in a cool place until wanted. The slides also, with the sections 

 attached, can be kept until it is convenient to stain, if preserved 

 free from dust in a slide box. 



Cover -glass and Film Specimens 



Cover-class and film specimens are used for the examina- 

 tion of cultivations of bacteria, and of blood or other 

 fluids or secretions, organs, etc., for the presence of micro- 

 organisms. 



Films and smears are now usually made on the slide, 

 but may be made on the cover-glass (" cover-glass speci- 

 mens "). In either case the glass must be clean and free 

 from grease. Cover-glasses must be thin, otherwise the 

 higher powers cannot be employed to examine the 

 preparations, and those described as " No. 1 " should 

 be purchased, " f-in. squares " being a convenient size. 

 These serve both for cover-glass specimens and for cover- 

 ing sections ; it is well also to have a few of the same 

 thickness but larger, viz. f-in. or 1-in. squares, for large 

 sections. Slides and cover-glasses may be cleaned by 

 boiling them in a porcelain dish with 10 per cent, carbonate 



