148 



the form of elements with a more and more intense dark 

 red and blackish-red colour. Not only the red, but also 

 the black staining can be produced by simple 

 fuchsin staining. 



As a general method of staining, as previously referred to, 

 I have employed Gram's method and it would be easy to look 

 upon the black bodies as Gram-positive. After examining a 

 number of cultures where such bodies were m'uch in evidence, 

 it was found however, that they could just as easily be stained 

 black by simple fuchsin staining (Ziehl-Neelsen's carbol-fuch- 

 sin diluted 1 -(- 9; 5 minutes staining without heating). 



It has been found that the black staining of these elements 

 is also produced by carbol-toluidin blue and to a less extent 

 by methylene blue and neutral red. (In all cases they were 

 stained 5 minutes). Further, they could be observed in Gram- 

 stained preparations without counterstaining. They are there- 

 fore elements with an excessive power of absorbing dyes. 



If these experiments give no other information we can 

 at least conclude from them that in an ordinary Gram-stained 

 preparation with counterstaining we are not justified directly 

 in regarding every black element as Gram-positive. (An ele- 

 ment which is stained black by Gram's method and by every 

 other method of staining can neither be called Gram positive 

 nor negative.* Some of the black stained spherical elements 

 could resemble Staphylococcus. That it is not a question of 

 contamination with Gram^positive cocci is proved partly by 

 the fact that they are also stained by fuchsin alone and partly 

 because these, or other elements of exactly similar appearance, 

 adhere to Gram-negative rods. 



These spherical elements are by no means specific for 

 Pfeiffer's bacillus although they seem to occur in greater 

 numbers in it than in other bacteria. In the whooping-cough 



Later addition: When preparations consisting partly of Gram- 

 positive bacteria (Staphylococcus) and partly of Pfeiffer's ba- 

 cillus with the black-staining granules, are treated with carbol- 

 fuchsin -j iodine in potassium iodide -j- alcohol -j- carbol- 

 fuchsin, that is Gram's method in which methyl violet is re- 

 placed by fuchsin (the staining then naturally ceases to be 

 Gram's method), the granules of Pfeiffer's bacillus were always 

 stained black while the Staphylococcus only took I he fuchsin 

 colour. 



