1890.] MICROSCOPICAL JOURISAL. 61 



BACTERIOLOGY. 



By V. A. MOORE. 



The Staining of Sections.* — Although it is sometimes possible 

 to sec under the microscope even single unstained bacteria lying 

 in the tissues, it is absolutely necessary for more exact examination 

 previously to stain them so that they are sharply defined from 

 the surrounding tissues. For this purpose aniline colors are used, 

 and of these there is not one which, when applied properly, can- 

 not stain the bacteria. This, however, is not alone sufficient, for 

 the chief desideratum is to stain them differently from their sur- 

 roundings, and if aniline colors, after the first trials, are regarded as 

 unsuitable, it is because one does not understand the proper way to 

 differentiate the bacteria in sections which had been diffusely stained 

 with them. The procedure of staining is, under some circumstances, 

 very easy, and under other circumstances very difficult. It is a ques- 

 tion not only of bringing into view all the micro-cirganisms, but also 

 the ascertaining with exactness their relations, and this is only possible, 

 when, by particular methods, we are able to make each individual part 

 of the tissue so distinguishable from another that they in some way be- 

 come also sharply defined from their surroundings. 



Putting aside the staining methods, which were designed from the 

 very first to stain the micro-organisms of a tissue only, leaving the 

 other parts unstained, attention has been, till now, devoted almost ex- 

 clusively to what are called good nuclear stains. These stains have, it 

 is true, many advantages, where only a good view of the tissue is re- 

 quired ; the disadvantage that the micro-organisms are covered by 

 deeply stained nuclei cannot, however, be denied. For bacteriologi- 

 cal purposes it is essential, above all things, to make the nuclei distin- 

 guishable from the other parts of the tissue, and I have tried to accom- 

 plish this end by methods which would stain the nuclei brightly, and 

 the protoplasm of the cells somewhat more darkly. Such a method in 

 no way interferes with the power of distinguishing the different tissues, 

 but the covering of any stained micro-organism by dark nuclei is 

 avoided. As a proof of bacteria in the vessels, this is, of course, of no 

 great importance, but it is for the cases in which the organisms lie in 

 the cells, or between them in cell-accumulations, as is the case, for ex- 

 ample, in tuberculous nodules. In such cases we can easily show by 

 comparative trials that preparations in which the nuclei are brightly 

 stained, many more micro-organisms can be seen than those in which 

 the nuclei are darkly stained. It is not the place to enter here into the 

 chemical and physical processes which take place during the staining ; 

 it is sufficiently evident that it is not a mere mechanical deposit of 

 staining stuffs. This is proved by the marked changes which often 

 appear to occur to the stains whereby new colors are produced, which 

 appear in many parts of the tissue. 



I will mention only the violet color of the fat-cells (Mastzellen) , when 

 the tissues are stained with methylene blue. Indeed, our knowledge 

 of physiological chemistry as well as of the so highly complicated 

 aniline compounds, is not enough to enable us to set ujd a sufficiently 



* Kuhne, Praktische Anieitung zum mikroskopischen Nachweis der Eakterien im terischeu Gewebe. 

 Translated by Dr . V. D. Harris, London, 1890, p. 8. 



