26 SPIROCHjETES. 



Of the actual structure of these tiny organisms little 

 can be said. An undulating membrane has been de- 

 scribed in some species, as by Gonder in Sp. vesperu- 

 ginis, by Prowazek in Sp. gallinarum, by Hoffmann in 

 Sp. buccalis, and by Schaudinn in Sp. refringens. On 

 the other hand, Levaditi denies that Sp. refringens 

 possesses an undulating membrane, and this structure 

 has never been seen or described in Sp. obermeieri, 

 Sp. pallida, Sp. muris, the spirochaete of ulcerating 

 cancer, etc. When it is borne in mind that one of 

 the favourite stains for spirochaetes, Giemsa's, 

 is deposited round, as well as in, the struct- 

 ures which attract it, it is easy to imagine a 



FIG. 13. FIG. 14. 



FIG. 12. Spirochaetaduttoni; appearance of a sheath. (Stephens.) 

 FIG. 13. Spirochaeta buccalis. Sheath. X22SO. (Prowazek.) 

 FIG. 14. Anthrax bacillus, with appearance of a sheath. (Ascoli.) 



possible source of error in observing this point in a 

 minute organism of spiral shape. Most of the illustra- 

 tions of undulating membranes in these small spiro- 

 chaetes are far from convincing. 



A definite sheath has been described in some forms, 

 e.g., in Sp. duttoni by Stephens (Fig. 12), in Sp. pallida 

 by Leuriaux and v. Geets, in Sp. buccalis by Prowazek 

 (Fig. 13), in the spirochaste found by Baruchello and 

 Pricolo in equine pneumonia, and in an unidentified 

 spirochaete found by Kenrick in a case of fever. An 

 appearance resembling a sheath, may be found in bac- 

 teria, as is shown in the accompanying illustration of 



