STAINING OF THE SECTIONS. 169 



In this method the sections are to be placed from 

 water into a solution of aniline-water gentian-violet, as 

 l^repared by the Koch-Ehrlich formula, Ijut which has 

 been diluted with about one-third its volume of water. 

 In this the sections remain for about ten minutes, pref- 

 erably in a warm place, at a temperature of about 

 40° C. They should never, under any conditions, be 

 boiled. 



From this they are washed alternately in the iodine 

 solution and alcohol, occasionally renewing the stained 

 with clean alcohol, until all color has been extracted 

 from them. They are then brought for one minute into 

 a dilute watery solution of eosin or safranin, or Bis- 

 marck-brown, again washed out for a few seconds in 

 alcohol, and finally for one-fourth minute in absolute 

 alcohol. From this they are transferred to xylol for a 

 half-minute. The remaining steps in the process are 

 the same as those given in the general method. In 

 some cases better results are oljtained by reversing the 

 steps in the process and staining the bacteria last, for 

 then the frequent decolorizing action of the alcohol on 

 the bacteria is diminished; thus, place the sections from 

 alcohol into eosin, safranin, or Bismarck-brown for a few 

 minutes, then wash out in 50 per cent, alcohol, then for 

 from three to five minutes in the dilute aniline-water 

 gentian-violet solution, then into the iodine bath, after 

 three minutes wash out in alcohol, and, finally, for one- 

 fourth minute in absolute alcohol, and then into the 

 xylol, from which they may be mounted. Some of the 

 organisms which may be stained by this method are 

 microcooeus tetragenus, b. diphtherice, b. anthraeis, and 

 staph, pyogenes aureus. It cannot be successfully em- 

 ployed with the bacillus of typhoid fever. 



