30 SPIROCIOETES. 



guishing and classifying these organisms. The exist- 

 ence of somewhat different forms side by side has been 

 already referred to in connection with Sp. anodontaz. 

 It is remarkable that two forms also exist together in 

 Tapes laeta (Sp. tapetos) and in other molluscs (Schellack) . 

 The coexistence of the two forms, Sp. pallida and Sp. 

 refringens, in syphilitic lesions is well known. Two 

 forms are described by Loewenthal in ulcerated cancers , 

 one larger and the other smaller, and two also by 

 Branch in cases of haemoptysis, and by Moritz in 

 decaying potato (5^?. polyspird). Castellani found 

 four forms associated in his cases of haemoptysis. 



The question of change of form has been most care- 

 fully studied in connection with S^. pallida. Bertarelli 

 and Volpino describe intermediate forms between Sp. 

 pallida and Sp. refringens, and Bosc suggests that 

 refringens is a degenerative form of pallida. Schere- 

 schewsky noted irregular forms of Sp. pallida in cul- 

 tures, and was struck by the resemblance of some of 

 these to refringens, and Sobernheim and Tomasoli also 

 observed irregular forms. 5^. pallida is noted for the 

 regularity of its curls and is indeed identified by this 

 means; yet Schaudinn observed that almost straight 

 forms might occur; Sobernheim and Tomasoli found 

 specimens with straight portions toward the centre ; and 

 Fouquet recorded the discovery of straight forms in 

 tertiary syphilis. Krzystalowicz and Siedlecki noted 

 changes in Sp. pallida by which individuals contracted 

 and thus became shorter and plumper. Eitner, who 

 observed living forms indistinguishable from Sp. pallida 

 noted that some of these straightened out when dead 

 and were thus differentiated. 



Krienitz studied the spirochaetes present in the stom- 

 ach and found that they underwent a change of form 

 according to alterations in their environment. He 



