ii6 MICROSCOPIC METHODS. 



i . PitfielcT.s Method as modified by Richard Muir. 

 Prepare the following solutions : 



A. The Mordant. 



Tannic acid, 10 per cent watery solution, filtered . 10 c.c. 



Corrosive sublimate, saturated watery solution . 5 c.c. 



Alum, saturated watery solution . . . . 5 c.c. 



Carbol-fuchsin (vide p. 113) . . . . 5 c.c. 



Mix thoroughly. A precipitate forms, which must be allowed to 

 deposit, either by centrifugalising or simply by allowing to stand. 

 Remove the clear fluid with a pipette and transfer to a clean bottle. 

 The mordant keeps well for one or two weeks. 



B. The Stain, 



Alum, saturated watery solution . . . 10 c.c. 



Gentian-violet, saturated alcoholic solution . . 2 c.c. 



The stain should not be more than two or three days old when used. 

 It may be substituted in the mordant in place of the carbol-fuchsin. 



The film having been prepared as above described, pour over it 

 as much of the mordant as the cover-glass will hold. Heat gently 

 over a flame till steam begins to rise, allow to steam for about a 

 minute, and then wash well in a stream of running water for about two 

 minutes. Then dry carefully over the flame, and when thoroughly 

 dry pour on some of the stain. Heat as before, allowing to steam 

 for about a minute, wash well in water, dry and mount in a drop of 

 xylol balsam. 



This method has yielded the best results in our hands. 



2 . Loffler's Method. 



Two solutions must be made up. Loffler gives the following 

 directions for their preparation : 



A. The Mordant. To 10 c.c. of a 20 per cent solution of tannin 

 in water add as many drops of a saturated solution of ferrous sulphate 

 in water as will give the whole fluid a dark-violet tint. To this add 

 3-4 c.c. of a solution made by boiling I gramme of logwood with 8 c.c. 

 of water (after boiling, filter and make up to 9 c.c. to compensate for 

 evaporation). The mixture of the tannin solution with the logwood 

 solution appears of a dirty dark-violet colour. If too much logwood 

 is added particles are precipitated which make the fluid useless as a 

 mordant. It is preferable to make up this mordant fresh on each 

 occasion of its use. The addition of 4-5 c.c. of 1-20 carbolic acid 



