74 ROPIXESS IX WATTLE BARK INFI'SIOXS^ 



for assisting in the production. Levuldsc and saccharose aic .yoodseconds. There 

 is a suggestion that suerase or invertase is secreted by tlie bactci-ia as saccharose 

 is the only biose that is utilised to any extent, but a search for this en/.ynie did 

 not show its existence. 



It is curious that the hexatomic alct)hol, manuit, should l)e so good, but it 

 seems to be peculiarly suitable for the i)roduction of many kinds of slime and is 

 ver\' frequently used in bacteriology for the nutrition of slime-forming bacteria. 



Dextrose probably acts (|uite as well as the other substances, but it seems to 

 be specially adajited to form a slime dissolving enzyme and on this account the 

 rope-producing action of the stigar is not so clearly shown. 



Glycerin is peculiar. It acts as a source of carbon for tne phase A'2 and 

 alters Al to this phase, it does not seiTe as a favourable nutrient for B2; in- 

 deed, it is not only unfavourable, but it also slowly changes B2 to the jihase Bl, 

 ■ind therefore acts in op]Josite directions with the two bacteria. Like mannit, it is 

 a general nutrient for the production of .slime from the majority of slinie-formiu^ 

 bactei-ia, as will be seen from a perusal of my papers upon slime-forming bac- 

 teria. 



Maltose, raffinose anil lactose may be considered as being ineapable of utilisa- 

 tion by the bacteria A and B. It is true that A2 can utilise them to some exten'^. 

 I)ut this phase is very active, and is able to make bouillon ropy, a fact which 

 should be considered in connection with the production of ropiness in the presence 

 of meat-extract. 



It is probable that with suitable nitrogenous and saline nutrients and suitable 

 conditions as regards acidity, the liacteria A and B are capable of fonning ropy 

 solutions from any source of carbon, and that the absence of the bacteria, rather 

 than an unsuitable pabulum, sho\dd lie the object aimed at in preventing ropiness 

 in wattle bark infusions. 



'///(■ fiifliD'nce (if Salts. 



It is customary to add salts to bacteriological Ihuds for tlie |)urp(ise of sup- 

 plying all those that may be necessary for the nutritiim of the bacteria and of 

 raising the osmotic pressure. The ordinary nutrient bouillon, agar and gelatine 

 contains J % of common salt together with the salts that may be contained in 

 the meat-extract used in the jireparation of the media. With this amount of 

 saline matter, the ordinary bacteria grow very well, but it does not I'olhiw that 

 this amount is best for all bacteria. Water and soil bacteria, for example, exist 

 upon nuich less, and it is a matter of common knowledge to the bacteriologist that 

 the saline content of bacteriological (luids can be raised or lowered considerably 

 without harming the bacteria to any great e.xtent. 



In the earlier experiments the saline matter had been \isually added to the 

 extent of ()..S %> ••"'! generally consisted of pota.ssium ])iiosphate 0.2 %. mag- 

 nesium sulphate, 0.1 ''/c, and calcium chloride. 0.02 %. As these may or may not 

 be good for assisting the bacteria in the production of the roiiy substance, a num- 

 ber of tests -were made to get some information upon the matter. 



In ah early experiment, a solution of glycerin, 2 %, and meat-extract, 

 0.25 %, was divided into portions, and each received 0.1 % of certain salts. 

 They were seeded with A. a mixture of Al and A2. Tiiat with calcium nitrate 

 seemed to give the most slime on the second day. After twenty days' incubjition 

 the slimes were coagulated with alcohol and weighed. The inilliai'anis nl' ash-free 

 slime ficr 100 c.c. of li(|uiil are given below:— 



