THE GENUS SPIROCHETA AND ALLIES 225 



Siebert's conclusion that they are products of periplastic dissociation, 

 or Prowazek's ('06), that they are dissociated myonemes, appears to 

 be the more probable explanation. 



C. The Spirochete Nucleus. — As already shown for Spirocheta 

 balhianii and Sp. anodontce, there is no definite morphological nucleus 

 in these forms, and the distribution of chromatin granules recalls the 

 condition of bacteria. Nevertheless, the occasional aggregation of 

 these granules into a heliform cord or the permanent rod form, as 

 in Sp. plicatilis (Schaudinn), indicates a higher organization than in 

 bacteria and a step toward the condition in protozoa, where, as in 

 tetramitus, there may be only granules which come together at periods 

 of division to form a loose but nucleus-like aggregate (Calkins, 1898). 

 The view expressed by MacWeeney, that spirochetes are all nucleus, 

 or chromatin only, brings back the controversy over the nature of 

 bacteria which has now been definitely settled, and it is unnecessary 

 to go over the matter again for these spirilliform types. • 



In the great majority of spirochetes that have been described more 

 or less minutely, no nucleus of any kind has been mentioned. In the 

 better-known forms, however, chromatin granules of one form or 

 another have been described somewhat fully. Bonhoff describes a 

 single brightly staining central granule in his Sp. vaccinw. In Sp. 

 recurrentis , the cause of relapsing fever, Novy and Knapp ('06) made 

 out no internal structures; the organisms "invariably gave a solid 

 stain, exactly as in the case of ordinary spirilla or bacilli" (p. 300). 

 But ordinary bacilli and spirilla do show internal structures, many of 

 them analogous to chromatin and interpreted as such by different obser- 

 vers (Biitschli, Schaudinn, etc.). So, too, the organism of relapsing 

 fever possesses granules which may be chromatin and may correspond 

 with the chromatin granules of Sp. halbianii. In the closely allied 

 Trep. gallinarum Prowazek ('06) finds local condensations which stain 

 like chromatin and which he interprets as such (his Fig. 6). Similar but 

 more numerous granules were observed by Dutton, Todd, and Tobey 

 ('06) in Spirillum (Spirocheta) duttoni, and by Carter ('06) in the same 

 species from the eggs of Ornithodorus moubata. Finally, in Treponema 

 pallidum, Krzysztalowicz and Siedlecki ('05-'08) have observed small 

 deeply staining granules which they regard as condensed chromatin 

 surrounding a clear space of "achromatin." (It might be pointed 

 out, however, that this observation might be used equally well in sup- 

 port of Swellengrebel's view of transverse division through the medium 

 of a cloison transversal.) Wechselmann and Lowenthal (1900) have 

 observed similar granules by aid of the ultraviolet light. Summing 

 up the evidence as to nuclei of spirochetes, it may be safely affirmed 

 that these primitive types of organisms possess nuclei in the form of 

 scattered chromatin granules which may come together at times to 

 form rod-like or sphere-like aggregates, a condition duplicated by the 

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