100 MICRO-ORGANISMS AND FERMENTATION. 



irregularly swollen cells make their appearance in the growth, 

 which under the existing nutritive conditions may probably 

 be considered as diseased or degenerate forms (involution 

 forms). More thorough investigation into this question is 

 to be desired. The forms noted by Hansen in the cycle 

 described have quite a different physiological significance, 

 for they are then developing freely, and thus preparing the 

 growth for the formation of new cells. 



Bacterium xylinum is essentially different from these three 

 species. It was described by Adrian J. Brown in 1886, who 

 examined it especially from a chemical point of view. It 

 forms a film, the slime of which becomes cartilaginous and 

 tough like leather. The growth, consisting of motionless rods 

 resembling Bad. aceti, gradually fills up the whole liquid. This 

 species is essentially different from the three first described 

 in another respect the slimy envelope shows the cellulose 

 reaction, which is not the case with the slime of Hansen's three 

 species. According to Emmerling the slimy sheath contains 

 an albuminoid substance resembling chitin. 



According to an investigation undertaken in the author's 

 laboratory, this species occurs in vinegar factories in many 

 countries in a vigorous state of development. According to 

 Henneberg, it may react unfavourably on the aroma of vinegar, 

 and by forming slime may arrest the quick vinegar process. 



The sorbose bacteria investigated by Bertrand, which 

 cause the conversion of sorbite, from the juice of mountain 

 ash berries (Sorbus aucuparia), into sorbose, is identical with 

 Bad. xylinum. 



Zeidler found an acetic acid organism in lager beer, Thermo- 

 bacterium or Bacillus zeidleri, which occurs as short motile 

 cells and involution forms. When a given quantity of acid 

 has been formed in the liquid, the movement of the cells ceases. 

 If the growth is sown on hopped wort, a cloudy turbidity 

 forms on the surface ; the whole liquid gradually becomes 

 turbid, and acquires a yellowish-brown colour. Small pro- 

 tuberances form on the surface of the liquid, which soon 

 sink, and thus a loose brownish deposit is produced. The 

 species does not appear to be dangerous in the brewery. 



Bacterium oxydans, a species with motile cells, was de- 



