70 THE AMERICAN MONTHLY [Feb. 



from it, are certain round or oval bodies which may be made 

 apparent by certain methods, the existence of which was 

 brought to our attention by Babes, Neisser and Ernst. The 

 method pursued by the last was to stain strongly with hot methy- 

 lene blue, and follow with bismarck-brown. These bodies would 

 be blue, the rest of the bacillus being brown. Dr. Crouch had 

 been investigating the feasibility of employing this peculiarity 

 of the diphtheria-bacillus to. differentiate it from other bacilli 

 found in the mouth, and with a degree of success beyond expec- 

 tation. He had found, likewise, simpler methods of staining 

 and peculiarities that he believed to have escaped attention 

 hitherto. 



If a fresh serum-culture is stained momentarily with a one per 

 cent solution of methyl-green, it is often possible to bring out 

 these bodies without further treatment. Treated thus they pre- 

 sent the appearance of reddish granules in a faintly green bacil- 

 lus, usually one at each end. By staining with methyl-green 

 more strongly and following with methylene-blue, bacillus with 

 red dots resembling spores will be seen. These bodies have ap- 

 parently a peculiar affinity for methyl-green, with which they 

 enter into a chemical combination, resulting in change of 

 color from green to red. Dr. Crouch had consequently em- 

 ployed methyl-green for their detection. B}' adding other 

 colors the penetration of the methyl-green may be increased, 

 and a double stain obtained immediately. Dahlia had been 

 found most useful, employed in the following proportions : 

 *One part of one per cent dahlia in water, five parts one per cent 

 methyl-green, and four parts water. If either color predomin- 

 ates in the stain too decidedly the other color is cautiously 

 added until the desired result, as tested on the bacilli from a 

 culture, is obtained. 



The stain works instantaneously, and if too deep the effect is 

 not obtained. In such a case the cover-glass may be treated 

 quickly with bismarck-brown, which replaces the dahlia in the 

 body of the bacillus, leaving the bodies described standing out 

 in contrast. Dr. Crouch had tested this method in a large 

 number of cases during the last six or eight months, and had 

 never failed to find the result of the culture positive when he 

 found these forms present in the cover-glass examination. In 

 one case in which he had diagnosticated diphtheria the first cub 



