INVESTIGATION OF AMERICAN STAINS 139 



as Macy and Robertson, who used aqueous solutions, obtained 

 essentially as good results with the zinc salt. The striking 

 exceptions to the inferiority of "mcthylen blue for bacilli" are 

 the samples from Coleman and Bell, and from the Heyl Chemical 

 Company. After completing the test, it was learned that these 

 two samples, although not labelled medicinal, and not claiming 

 to meet the U. S. P. requirements, are fairly free from zinc, 

 having been especially purified and corrected for bacterial 

 staining. 



Of the samples of medicinal methylen blue, six stand at the 

 top, as a stain, with the honors quite evenly divided between 

 them: namely, Calco, dealer C, WiUiamsburg, Coleman and 

 Bell, Heyl, and Providence. Almost as good are the Goldin 

 and H. S. samples. Of these eight companies, we find that the 

 Calco Chemical Companj', the Coleman and Bell Company, the 

 Heyl Laboratories, the Providence Chemical Laboratories, and 

 the H. S. Laboratories are making special efforts to put out a 

 pure product well adapted to both staining and therapeutic uses. 

 It is plain that they are succeeding in this, so far as staining 

 properties are concerned, and provided the quaUty of their 

 products is maintained any of them may be used as a stain 

 without question. 



One fault found with certain samples of methylen blue is that 

 they have a tendency to dissolve milk smears off the slide when 

 used for the Breed method. The chemical explanation of this 

 phenomenon has not been obtained. The samples giving this 

 trouble were the zinc salt sample from Dicks, David and Com- 

 pany, and the medicinal samples from Harmer Laboratories, 

 MalUnkrodt Chemical Company, and from dealers A and B. 

 It is interesting to notice that these same samples have been 

 graded lowest according to their staining properties. They 

 are plainly not to be recommended. 



There is little correlation between the results of the staining 

 tests and those obtained by Levine with the eosine-methylen- 

 blue medium. The samples from dealer A, for instance, which 

 stood low as regards staining properties were among the four 



