484 SUMMARY OF CURRENT RESEARCHES RELATING TO 



organism i.s pointed towards an unseen centre, and the flagella take 

 ordinary stains readily; rosette formation is favoured by culture on 

 glucose agar under anaerobic conditions. The unattached organism is 

 actively motile, the flagellnm varying in length from two to five times 

 that of the single cell ; the rosettes are non-motile. The organism is 

 reproduced by transverse division ; spore formation was never observed ; 

 it does not stain by Gram ; growth on gelatin shows creamy white to 

 yellow colonies, and there is slow late liquefaction of the medium ; in a 

 gelatin stab, a third of the medium is liquefied after a month ; grown 

 in glucose agar, it formed no gas, but the flagella were much elongated ; 

 litmus lactose agar is decolorised after 2 weeks, but no alteration 

 occurs in neutral red agar ; on blood serum at 87° C. there is formed a 

 delicate glistening, slightly opaque line, and occasionally distinct round 

 colonies 8 mm. in diameter ; no liquefaction of the medium occurs ; on 

 potato it forms moist patches, and shows many involution forms, but no 

 rosette formation ; broth cultures are uniformly clouded after 24 hours 

 at 37° C, and show a blue-white pellicle clinging to the walls of the 

 tube ; hanging drops show abundant rosette formation : litmus milk is 

 decolorised after 3 weeks, and after 44 days it becomes intensely alka- 

 line and very viscid ; indol formation was not observed ; no fermentation 

 takes place when grown in dextrose, saccharose, or lactose ; it is a 

 potential anaerobe, but growth is slower and less abundant in the absence 

 of oxygen ; its optimum temperature is 37° C. ; it is killed by moist heat 

 at 55° C. for 10 minutes ; experiments to test its pathogenicity on 

 guinea-pigs and pigeons were negative. 



Bacterial Niveau of Beijerinck.* — K. B. Lehman and H. Curchod 

 have studied the formation of these niveaus in B. typhi, B. coli, Vibrio 

 cholera, B. pyocyanem, and others. The term " niveau " is applied only 

 to a collection of bacteria stretching as a horizontal skin across the fluid 

 of the tube ; besides the niveau they also distinguish the diffuse cloudi- 

 ness of more or less compact collections of bacteria that are formed either 

 above or below the niveau ; between the niveau and the cloudiness there 

 is a more or less well developed clear zone. They employed the follow- 

 ing method : — 5 c.cm. of ordinary nutrient gelatin was poured into a 

 sterile tube, and, after solidifying, this was inoculated with a pure culture 

 of an organism and covered with 16 c.cm. of sterile distilled water, so 

 that the surface of the water stood at the height of about 8 cm. ; the 

 tubes were placed (upright) at room temperature and guarded against 

 shaking. 



With B. typhi, B. coli and B. putidus the niveau is well developed 

 after 24 hours, and above it is seen a strong cloudiness ^ cm. high which 

 is not separated from the niveau by any clear zone, and which disappears 

 after 2-3 days ; below the niveau, especially with B. typhi and B. coli, 

 there is a thick cloudiness ; with Vibrio cholera there is a cloudiness 

 above and below the niveau, but the niveau lasts at most only 18 days. 



AVith B. pyocyaneiis there is at first a thin niveau with an underlying 

 cloudiness and no intermediate clear zone, but after the seventh day, 

 when the niveau has risen to its highest point and has begun to sink, a 

 cloudiness commences to form above the niveau. 



* Centralbl. Bakt., 2 to Abt. xiv. (1905) p. U9. 



