58 THE AMERICAN MONTHLY [February, 



BACTERIOLOGY. 



Stainingthe Capsules on the Micrococcus Lanceolatus. — 



Prof. Welch {JoJms Hopkins Hospital B 7/ He tin, ni{i8g2), p. 

 12§) has described a new method for staining the capsules on the 

 jSIicrococais lanceolatus. It is as follows : Cover-glass prepara- 

 tions made without water from the tissues of rabbits or other ex- 

 perimental animals dead from the inoculation of this germ are 

 treated first with glacial acetic acid, which is at once allowed to 

 drain oft'and is replaced (without washing in water) with aniline- 

 oil, gentine-violet solution. The staining solution is repeatedly 

 added to the surface of the cover-glass until all ()f the acid is dis- 

 placed. If now the specimen is washed with a saturated aqueous 

 solution of the common salt and is examined in this solution, it 

 will be seen that both coccus and capsule are uniformly and deeply 

 stained and cannot be dift'erentiated. If water be used instead of 

 saturated salt solution, the capsules are decolorized, sometimes 

 only in part when they can be clearly recognized, but often com- 

 pletely, and tiiey may entirely disappear. By using weak solu- 

 tions of salt it is possible in all cases to difl'erentiate the capsule 

 if it is present. The strength of the solution best adapted to dif- 

 ferent cases varies. Often the ordinary physiological solution 

 suffices. A generally useful strength is two per cent. The speci- 

 mens are to be examined in the salt solution. When mounted in 

 balsam the capsules do not always remain distinct. The capsules 

 may appear stained throughout, or only their outer margin may 

 be stained. This method of staining was worked out on the sup- 

 position that the capsules are composed essentially of mucin, which 

 is precipitated by acetic acid, and when thus precipitated is in- 

 soluble in concentrated salt solution and swells up in water. The 

 chief advantages of this method are the difficulty of avoiding pre- 

 ci23itates of the dve, and the alterations in the cells and other ele- 

 ments, but in difficult cases it will serve a useful turn, although 

 less violent methods when applicable are to be preferred. 



The capsules vary in their structure, some being much more 

 delicate and narrower than others. In old exudates the capsules 

 are often very distinct and resistant to the action of water, in which 

 they may appear even quite highly refractive. The Micrococcus 

 lanceolatus stains readily on cover-slip preparations with the ordi- 

 nary aniline dyes. It is less easily stained in sections. In these 

 it can be stained by Gram's method, but Weigert's fibrin stain 

 gives better results. The number of cocci brought to view by this 

 last method in sections of human lungs atlected with lobar pneu- 

 monia is often very great, and the presence of the majority of the 

 cocci inside of leucocytes is clearly demonstrated. 



Some Facts about Lustgarten's Method for Staining 

 Syphilis Bacilli. — M, Sabouraud (Annales Inst. Pasteur, 1S93, 



