140 H. J. CONN 



best samples in this medium. The medicinal sample from the 

 Providence Laboratories, on the other hand, proved good for 

 staining but unsatisfactory in this medium. The five samples 

 grading good or very good as stains and also proving good or 

 very good as an indicator were the two Coleman and Bell samples 

 and the medicinal samples from the Calco Chemical Company, 

 AMlliamsburg Chemical Company, and from dealer C. Those 

 samples proving unsatisfactory were condemned because of 

 toxicity. Strange to say, as many medicinal samples as zinc 

 salt samples proved toxic, although for medicinal purposes the 

 zinc salt alone is condemned on account of toxicity. In fact, 

 for this medium, the zinc salt seems to prove almost if not quite 

 as good as the free chloride. 



There can be no question that, so far as our data go, one of the 

 five samples just mentioned as satisfactory for both purposes 

 should be recommended. The Heyl samples seem to rank with 

 these as to staining properties, but for the reasons mentioned 

 in the introduction, could not be included in the early tests, 

 so we do not know how satisfactory they would prove in the 

 Levine medium. We have not learned the original source of the 

 sample from dealer C. The Williamsburg sample was labelled 

 medicinal, but proves not to be entirely zinc-free. As a result, 

 the composition of this product may well have been changed by 

 the present time to meet U. S. P. requirements, and one could not 

 count on getting another sample like the one tested. The two 

 Coleman and Bell samples and the Calco medicinal sample all 

 give very good results, and are produced by companies we beUeve 

 to be reliable and to supply nothing but distmctlj' American 

 products. Both companies we understand to manufacture 

 their owti methylen blue from American-made cnides or inter- 

 mediates. Any of these three samples can be used with entire 

 confidence of obtaining good results. Of these three, the Cole- 

 man and Bell "methylen blue for bacilli" has two pomts 

 especially in its favor: it is not quite so expensive as the U. S. P. 

 preparations, and it is the best of these three samples in the 

 Levine medium. 



