■24 THE AMERICAN MONTHLY [Feb 



lodioii mettiod has been described heretofore. The sec- 

 tions are fastened to the slide by putting a few drops of 

 ether and alcohol on the section after it is in position. 

 Use a mixture of three parts ef xylene and one part of 

 castor oil as a clarifier. In passing a section from 

 water to strong alcohol, or vice versa, avoid the diffusion 

 currents by plunging th3 slide directly into the desired 

 liquid instead of carrying it through successively higher 

 or lower percentages of alcohol. 



We want a suitable dye that will stain the bacteria 

 properly and yet one that will wash out of the imbed- 

 ^ding material without the use of a decolorizing agent so 

 strong that it will remove the stain from the tissue and 

 the bacteria. Having some sections that I wanted to 

 stain with gentian violet, but being out of it, I substi- 

 tuted dahlia. These sections had been cut by the paraf- 

 fin method and the stain not only showed the bacteria 

 well but brought out the histological structure of the 

 tissue. Later, I cut some sections from material which 

 had been imbedded in collodion and stained them for 

 bacteria. After trying carbol fuchsin and methyl violet, 

 I tried an aqueous solution of the dahlia. It worked 

 perfectly. In the process of washing and dehydrating 

 this was entirely removed from the collodion, leaving 

 both the tissues and the bacteria well stained and sharp- 

 ly differentiated. 



Other formulas, using dahlia as the dye, were unsatis- 

 factory, such as a solution containing less of the elements 

 of a mordant nature, using 2 per cent, carbolic acid 

 instead of 5 per cent., which did fairly well and also 

 Koch-Ehrlich's aniline water solution which stained the 

 collodion too deeply. The formula for the stain used is : 

 Saturated alcoholic solution of dahlia 20 cc; distilled 

 water 100 c c. The length of time varies, according to 

 the condition of the tissue, from fifteen minutes to half an 

 hour. They must be distinctly overstained. Wash thor- 



