Uses and Standardization of Stains 15 



A comparatively new field is now bacterial cytology. As in the 

 case of histochemistry, development in this field has been made 

 possible by improved methods of fixation. The conventional 

 method of rendering bacterial cells stainable was merely to dry 

 them on a slide, a process which distorts the cell and makes inter- 

 nal structure quite diflficult to demonstrate. Such crude fixation 

 methods are now being replaced, for all delicate work, with others 

 that cause less distortion ; and gradually bacterial cytology is being 

 revealed. There are difficulties still to be surmounted; artefacts 

 and true nuclear structures are sometimes difficult to tell apart, 

 and misinterpretations are frequently made. Nevertheless, the 

 field is being rapidly explored, and the subject of bacterial cytol- 

 ogy is no longer so highly speculative as it was a comparatively 

 few years ago. 



Bacteriological staining methods (outside of cytology) can be 

 divided into two groups: stains for bacteria in dried films; and 

 stains for bacteria in tissue. The former consist of very simple 

 procedures, ordinarily; about the most complicated of them is the 

 Gram stain which calls for crystal violet and a counterstain; some 

 species of bacteria taking the violet stain, others, the counterstain. 

 The stains for bacteria in tissue are essentially histological methods, 

 many of them very similar to those used for general animal tissue; 

 their main purpose, however, is not the differentiation between 

 different tissue elements but that between bacteria and the tissue 

 in which they are located. 



An important aspect of bacterial staining is the laboratory 

 diagnosis of disease. In numerous diseases, of which tuberculosis 

 and diphtheria are the most conspicuous examples, staining pro- 

 cedures play a prominent role in diagnosis. So important is this 

 use that in spite of the smaller number of staining methods em- 

 ployed by the bacteriologist, he orders stains by the kilo while the 

 zoologist may content himself with 10-gram bottles. This is the 

 real reason why the bacteriologist is the chief customer of the 

 biological stain company. 



BIOLOGICAL STAINS IN TIME OF WAR 



The last mentioned use of stains has made them a very im- 

 portant war commodity. The first World War proved this. Be- 

 fore that war practically all dyes had come from Germany, and no 

 biological stains were considered reliable unless they bore the label 

 of one particular German company. In 1914, the blockade of 

 Germany prevented its dyes from going overseas and biologists 

 in many other countries began to wonder where they would get 

 fresh supplies of stains when the stocks of German dyes on hand 

 at the beginning of hostilities were exhausted. In America this 

 did not prove an immediate problem, for those stocks were quite 

 large, partly in the hands of the users and partly in the store- 



