610 president's address. 



formation of slime, gum or mucilage by bacteria is otherwise 

 than an advantage to the plant. It may be that it is only an 

 abnormal production that is injurious and makes itself evident 

 as a gum — or slime — flux. An investigation of the gum of Lin- 

 seed mucilage and of the gums produced by bacteria isolated 

 from the tissues of the plant, showed that one or two of the 

 microbes formed gum so similar to Linseed gum as to point to its 

 having been originally formed by the bacteria and subsequently 

 altered by the plant to mucilage. In reviewing the work that 

 has been done in the Society's laboratory, upon the production 

 of gum, it will be noticed that the majority of the bacteria are 

 very closely allied; the only differences being in the nature of 

 the srums aud the cultural characters which are influenced bv the 

 gums. It has been found that their typical faculty alters under 

 certain circumstances, and it is, therefore, probable that the 

 group originally consisted or consists of one type-species, the 

 physiological activity of which has been or can be modified by a 

 host-plant. Bacteria are to a certain extent classified by their 

 action while growing upon gelatin media, which they either do 

 or do not liquefy. A microbe which brings about a hardening of 

 the medium is a novelty, and such a microbe has been described 

 by our bacteriologist. Another curiosity which he brought 

 forward was a bacterium which had attached to it capsular 

 structures like lateral wings. 



In another branch of bacteriology, Dr. Greig-Smith has indi- 

 cated that the immunity which we all possess against the multi- 

 plication of the putrefactive bacteria may have its origin in the 

 slow but continued passage of these bacteria across the wall of 

 the intestinal tract. The result is as if we were being continu- 

 ously vaccinated with these bacteria. Within the tissues and 

 vessels of the immune animal, bacteria are destroyed either in 

 the fluids or within the phagocytes. The mobile leucocytes can 

 readily ingest harmless bacteria, but the same facility is not 

 exhibited towards those which are virulent. From a considera- 

 tion of the physical relation betw^een a microbe and a mobile 

 phagocyte, it appeared probable that if the former were covered 



