162 BACTERIOLOGY. 



The section must be lifted from one vessel to the 

 other by means of either a curved needle or a glass rod 

 drawn out to a fine end and bent in the form of a curved 

 needle. 



By the above process of staining, which can be prac- 

 tised as a routine method for most bacteria in tissues, 

 the nuclei of the tissue cells, as well as the bacteria, will 

 be more or less deeply stained. 



SPECIAL METHODS OF STAINING BACTERIA IN 

 TISSUES. For purposes of contrast stains it sometimes 

 becomes necessary to completely, or nearly completely, 

 decolorize the tissues and leave the bacteria unaltered 

 in color. For this purpose special methods depending 

 on the staining peculiarities of the bacteria under con- 

 sideration have been devised. 



Gram's method with tissues. One of the most com- 

 monly employed differential stains is that of Gram. In 

 general, it is practised in the way given for its employ- 

 ment on cover-slip preparations, with some slight modi- 

 fications. 



In this method the sections are to be placed from 

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

 as prepared by the Koch-Ehrlich formula, but which 

 has been diluted with about one-third its volume of 

 water. In this the sections remain for about ten min- 

 utes, preferably 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 safrauin, or Bismarck- 



