BY R. GREIG SMITH. 37 



The precipitate obtained on the addition of alcohol to a 

 suspension of the gum or slime in water is exceedingly 

 voluminous ; a precipitate which occupies a volume of about 50 

 CO. becomes, after squeezing out the dilute alcohol in a calico 

 strainer, a small pellet measuring about a quarter of a c.c. On 

 precipitating the aqueous suspension three or four times with 

 alcohol an opalescent alcoholic solution is obtained, from which 

 the gum can be precipitated by small quantities of neutral salts, 

 such as sodium chloride. This fact, together with the reactions 

 obtained with some of the albuminoid reagents, suggested the 

 similarity of the gum to the mucins. That the zooglcea slime of 

 , bacteria consists of mucin, or a substance nearly allied to it, has 

 already been suggested, but there are many points of difference 

 between the bacterial slime and the mucins. The crude gum 

 obtained by precipitating the cultures with alcohol contains 6'1% 

 of ash and 3*08% nitrogen in the ash-free, dry substance. Repeated 

 precipitation with alcohol, and also filtration of the gum from the 

 accompanying bacteria, would undoubtedly lower this percentage. 

 It is, therefore, apparent that the nitrogen content alone is 

 sufficient to distinguish the slime from mucin or the allied 

 mucinoids. 



The identity of the bacterial slime with cane-gum proves con- 

 clusively that the isolated bacterium is the direct cause of the 

 gummosis of the plant, and also that the gum is no secretion of the 

 plant upon which the bacteria live saprophytically. Since this 

 applies to the gummosis of the sugar-cane, it probably also applies 

 to the gummosis of the vine and other plants, in which case 

 Mangin and Rathaj'- are wrong in considering that the action of the 

 bacteria in causing gummosis of the vine is very problematical. 

 Cane-gum is nitrogenous, and when a clear filtered solution is 

 exposed to the air it speedily produces a luxuriant growth of 

 foreign organisms. These undoubtedly feed upon the gum, and 

 it is possible that this observation gave rise to the idea that the 

 bacteria in the vessels of the plant live upon the gum. 



