76 Profs. H. Marshall Ward and J. Eeynolcls Green. 



sugar (saccharose) as a food material, probably by inverting- it. And 

 nevertheless the bacterium nourishes in conjunction with the living 

 yeast in saccharose solutions. Here is a puzzle which we have not 

 succeeded iu explaining. 



It may be merely noted that numerous trials were made in other 

 media than those mentioned, among which glycerine and yeast extract, 

 alcohol with saccharon and yeast extract, starch treated with diastase, 

 also potato, carrot, and milk are the most important. No growth of 

 significance Avas obtained in any case, and the results may be neg- 

 lected. 



The Acidity of the Cultures. 



Several tests showed that the cultures of the bacterium are acid, 

 and the following experiments were made. Sterilised blocks of marble 

 were 'placed in the culture tubes before they were steamed, and then 

 the infections made as before. In saccharose yeast extract, the active 

 growth which resulted was accompanied by a more diffused viscosity 

 than before, and gas bubbles (C0 2 ) ascended for days. Tubes of mixed 

 dextrose and levulose with yeast extract, treated exactly similarly, 

 became turbid, and gave off bubbles, but no trace of viscosity resulted ; 

 the abundant flocculent deposit consisted entirely of the non-sheathed 

 form of the bacterium. 



As will appear later, the acid which causes this liberation of COo is 

 mainly acetic acid. 



On the Nature of the Gelatinous Matrix or Slime. 



A number of experiments were made to determine the nature of the 

 viscous slime and the jelly-like matrix holding the bacteria. Although 

 reasons have already been given for concluding that this is really 

 nothing more than the swollen cell-walls or sheaths investing the 

 bacteria, the possibility of the opalescence and viscosity of the saccha- 

 rose media being due to the direct action on the sugar of some enzyme 

 or other body excreted by the organism requires investigation, for it is 

 conceivable that such slimes might arise in any of three ways. 



(1) As products of metabolism from the interior of the cells, such as 

 certainly occur in the glands of higher plants, e.g., the mucilage hairs 

 of ferns.* 



(2) As products of the action outside the cells of some enzyme-like 

 body which escapes from the organism and acts directly on the sugar. f 



(3) As products of conversion of the cell-walls of the organism, 

 these swelling up and becoming diffluent as in the case of the ginger- 

 beer plant. | 



* See Gardiner and Ito, ' Annals of Botany,' vol. 1, p. 27. 

 f See Kitsert, ' Cent. f. Bakt.,' vol. 11. p. 830. 

 X ' Phil. Trans.,' B, 1892, loc. cit. 



