GENERAL CHARACTERS OF SPIROCH^TES. 25 



homogeneously like bacteria. In some a vacuolated 

 structure may be made out, resembling that seen in 

 some of the larger spirilla. In the larger bacteria also 

 granules or masses of staining material may be seen, not 

 unlike those in Sp. anodontce (see Figs. 8, 9, 10). Fila- 

 ments of algae may also show features bearing a close 

 resemblance to some of those described in spirochaetes 

 (Fig. n). 



In the case of the smaller spirochaetes the minute 

 size of the organisms renders the investigation of their 

 intimate structure almost impossible. The general 

 shape is the same as that of the large varieties, accord- 

 ing to most writers, but it is even more difficult to 

 make sure of their flattened shape than in the larger 

 organisms. Some are definitely stated to be round in 

 section, e.g., Sp. pallida, but many authors follow 

 Vuillemin and Schaudinn in placing this and a few 

 others in a separate genus, Treponema, partly on this 

 account. 



The movements of the small spirochaetes are the 

 same as those described above. An additional form 

 of movement is, however, described by Plaut in Sp. 

 vincenti and called by him "euglenoid" movement: 

 it consists in the appearance of a thickening at one 

 point in the body of the organism and the gradual pas- 

 sage of this swelling from one end to the other. Krzys- 

 talowicz and Siedlecki describe a somewhat similar com- 

 pression and extension of the body of Sp. pallida when it 

 is in motion. It must be remembered that in these mi- 

 nute thread-like organisms it is impossible to distinguish 

 under the microscope between rotatory movement and 

 undulation. Lashing movements are said to be less 

 marked in treponema: indeed, the movements Sp. 

 pallida (Trep. pallidum) are altogether sluggish. 



