4 JOURNAL OF THE [January, 



a flame, has been the coagulation of albuminoids in the liquid of 

 the drop, to prevent general coloration of the field during stain- 

 ing. But this is the common cause of resistance to staining by 

 delicate inner details and the cilia, while it can be well effected 

 by immersion in a proper fixative. A second purpose of this 

 excessive drying has been the supposed necessity to insure 

 adherence of the film to the cover. But I have found that when 

 a film is well dried at low temperature, as explained beyond, no 

 peeling away or loss afterward occurs. 



4. The staining is irregular and unsatisfactory. In most bac- 

 teria mounts, as met everywhere on exhibition, these forms are 

 greatly overstained and look all alike, presenting mere silhouettes 

 of the contours, with few or no traces of inner structure and with 

 cilia entirely invisible. For a long time it has seemed to be the 

 acme of effort to render tliese microbes visible at all. This has 

 been followed by special efforts to effect satisfactory staining of 

 spores or of cilia, in separate preparations. Nor is it strange that 

 many bacteriologists have concluded that these silhouettes show 

 the prevalence of such a sameness of form among the kinds of 

 bacteria that the main dependence, for discrimination, must be 

 placed on other characteristics of a physiological nature, modes 

 of growth on different media, etc. 



But these opaque caricatures of the bacteria are as unworthy of 

 modern science and as unnecessary as similar misrepresentations 

 of the infusoria or other micro-organisms would be considered. 

 The improvement of modern lenses of wide aperture, and increas- 

 ing facility in their manipulation, are gradually leading as well to 

 more successful approach toward the i)reparation of an ideal bac- 

 teria mount. This should of course present the groups or chains 

 dispersed over the whole cover, with natural arrangement undis- 

 torted and unbroken, with normal mode of interconnection, and 

 with constituent rods or cocci just sufificiently stained to display 

 both inner structure and external organs. To this end the anilin 

 stains are commonly misused, being greedily and excessively ab- 

 sorbed by the plasm within the cells, while cellulose, callose, etc., 

 remain unaffected. With a dried bacteria film, therefore, the 

 preliminary use of some mordant is indispensable for staining, to 

 restore the absorbence in all parts of the organism. 



However, it is probable that the drying and heating of the bac- 



