540 BACTERIOLOGY. 



thus assists in the differentiation. This is especially true 

 when it is used in Gram's method. All trace of the oil, 

 however, must be removed from the section by washing- in 

 xylol. Some stains, like methylene blue, are readily dis- 

 solved by the essential oils, and in such instances the oil 

 can be omitted. The dehydrated section in that case is 

 placed direct in xylol. 



In some instances the treatment with xylol is dispensed 

 with. Thus, the section may be transferred direct from oil 

 of origanum to a glass slide. After wiping- off the excess 

 of oil around the specimen, a piece of filter-paper is firmly 

 pressed down on top of it. This is done several times until 

 all the oil has been removed. The flattened section is now 

 treated with balsam and covered. 



When transferring- the specimen on a spatula, care 

 should be taken to keep the clean surface of the instrument 

 evenly moistened with the liquid in which the section lies. 

 The spatula is slipped under the section which is then 

 drawn up on the blade by means of a needle. To remove 

 the section from the spatula to a liquid requires no 

 special care. When the section, however, is to be trans- 

 ferred to a slide a drop of the liquid, xylol or oil, should be 

 first placed on the center of the slide. With the end of the 

 spatula resting- in the drop the section is drawn down by 

 the needle, till a portion of it rests on the slide. By hold- 

 ing- this portion of the section with the needle the spatula 

 can now be easily withdrawn. 



Instead of using- the ordinary dilute anilin dyes, Lsffler's 

 or Kiihne's methylene blue and dilute Ziehl's solution may 

 be used. Thus, Pfeiffer stains the section for half an hour 

 in dilute Ziehl solution, then transfers it to absolute alcohol 

 which is very slig-htly acidulated with acetic acid. When 

 the originally dark-red section changes to a peculiar red- 

 dish violet color, it is cleared up at once in xylol and 

 mounted in balsam. 



In staining sections it is advisable not to overstain too 



