174 MICRO-ORGANISMS AND DISEASE [CH. ix 



way, to boil the film cover-glass specimen in the dye (methyl- 

 blue, gentian violet, or carbol fuchsin) ; hereby the spores 

 become deeply stained and on subsequent good washing 

 retain the dye with great persistence. By careful washing 

 the point may be so hit off that the spores appear deeply 

 stained, whereas the bacillary substance is only faintly so. 

 The finest specimens are obtained by boiling the dried film 

 specimen in carbol fuchsin ; then wash well in water ; then 

 place the specimen in methyl-blue anilin water for half a 

 minute to one minute ; wash again well ; dry and mount in 

 xylol balsam : the bacillary substance appears blue, the -spores 

 bright red. 



It has been shown by Engelmann that the presence and 

 renewal of oxygen as well as a certain concentration of the 

 nutritive material are essential for the motihty of those bacteria 

 that are possessed of cilia, i.e. that are possessed of locomo- 

 tion and which normally grow aerobically. This, of course, 

 does not apply to the motile anaerobic bacilli, e.g. bacillus 

 of malignant oedema, tetanus, or butyricus. 



As long as the bacteria are living, their protoplasm does 

 not combine (stain) with nitrate of silver solution, only after 

 death does this become possible. Hereby an index is 

 furnished for ascertaining whether, and which, bacteria in a 

 given sample are living, and which are dead. There is no 

 difference in this respect, i.e. in respect of the different 

 reaction of nitrate of silver on living and dead protoplasm, 

 between the protoplasm of bacteria and that of other vege- 

 table or animal tissues. 



All aerobic bacteria, pathogenic and non-pathogenic, 

 requiring for their growth and multiplication oxygen, obtain 

 this from the medium in which they grow, and which oxygen 

 is dissolved in those media, or after this is consumed or 

 absent it is obtained by the bacteria in the process of the 

 chemical decomposition of the carbohydrates and proteids 



