4 THE MORPHOLOGY OF BACTERIA 



that the flexible spirochetes can pass filters more easily than other forms of bacteria. 

 On numerous occasions bacteriologists have found that the effluent from the finest fil- 

 ters may yield species like the original on cultures, although organisms cannot be 

 found on microscopic examination. At the same time the effluent from suspensions of 

 pathogenic organisms may produce disease in animals although organisms cannot be 

 found on examination, or obtained in cultures. Unexpected results of this character 

 were usually attributed to defects in the filter material permitting a small number of 

 viable organisms to pass, or to a prolonged time in the process of filtration which per- 

 mitted motile organisms to penetrate the filter mass, or viable bacteria to grow through. 

 It was eventually recognized that this type of explanation did not always suffice to 

 explain the results and that other possibilities must be considered. 



Theoretically, the bacterial cell may at times develop into morphological minia- 

 tures of the original but with dimensions only fractions of the standard, or it may pro- 

 duce a kind of spore or seed within its waUs, visible, filterable and viable, but morpho- 

 logically unrecognized except as granules of characteristic size, shape, and staining re- 

 action. Finally, the bacterial cell as we see it ordinarily may be but one stage in a 

 complicated life-cycle, another stage being represented by filterable units, invisible by 

 present methods, but viable in cultures, or viable only in the human or the animal 

 body. 



While Schaudinn in his investigations of protozoa and spirochetes anticipated 

 theoreticaUy much of the work of more recent years and expressed his belief that cer- 

 tain species produce units which can pass filters, Gotschlich, as mentioned above, was 

 the first to emphasize the possibility of minute units among the simpler bacteria. In 

 his most recent publication Gotschlich' accepts filterable forms of bacteria as demon- 

 strated and states that they may be differentiated from the filterable and inanimate 

 products of bacteria by the fact that they are viable, in some instances capable of 

 growth and culture, and in other instances capable of producing a characteristic dis- 

 ease picture in experimental animals. With bacteria obviously too large to pass 

 through filters Gotschlich again emphasizes his earlier opinion that a fractional part 

 of the cell may escape and a normal adult cell regenerate from this portion. A vast 

 amount of work has been carried out to substantiate views of this nature, among 

 which may be mentioned the extensive studies of life-cycles of bacteria by Almquist, 

 Enderlein, Fuhrmann, Lohnis, Mellon, and others. Of especial importance in this im- 

 mediate connection is the work on the tubercle bacillus. 



Much^ in 1907 found small gram positive granules in the tubercle bacillus forming 

 an integral part of the cell and which can be recognized outside it by their peculiar ap- 

 pearance. With material containing these granules and no regular tubercle bacilli. 

 Much believed that he had produced tuberculous lesions in experimental animals from 

 which the characteristic acid fast organisms could be obtained. A little later Fontes^ 

 pointed out that the Much granules are able to pass through Berkefeld candles. He 

 inoculated guinea pigs with filtered granules and found no lesions except in the spleen. 

 With spleens from the first series of guinea pigs he inoculated another series, the ma- 



' Gotschlich, E.: Handb. d. path. Mikroorg., i, 33. 1927. 



» Much, H.: Beitr. 2. Klin. d. Tuherk., 8, 85. 1907. 



»Fontes, A.: Centralbl.f. Bakleriol., Abt. I, Ref., 51, 244. 1912. 



