ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 737 



worthy. (3) That natural immunity, especially towards the bacteria 

 that normally inhabit the intestinal tract, is occasioned and maintained 

 by the comparatively few bacteria which, in crossing the intestinal wall 

 and possibly gaining access to the body fluids and organs, stimulate 

 the cells to produce immune bodies. (4) That the agglutination of 

 bacteria may play a much more active part in the production of immunity 

 than is generally supposed. 



Bacteria and the Gum of Hakea Saligna.'"" — R. Greig Smith finds 

 that of the bacteria occurring in the tissues of this plant, the most 

 probable producer of the gum is one intermediate between B. acacice and 

 its variety B. metarabinum ; but as we do not yet know that the host- 

 plant can alter a gum once formed by a bacterium, it cannot be said that 

 the gum is produced by this micro-organism. 



Bacteria and the Gum of Linseed Mucilage.f — R. Greig Smith 

 found that the gum bacteria in Linum are very numerous, and consist 

 chiefly of two species. 



(a) Short motile rods, from " 3-1 ■ /* long, with many peritrichous 

 flagella, and not staining by Gram ; producing on glucose-gelatin plate 

 yellowish-white raised colonies with irregular margins ; in stab culture 

 there is a filiform growth in the track, and a broad nail-head at the 

 surface, which sinks later in the liquefying medium. Grown in broth, 

 it produces turbidity, a loose pellicle, and a coherent sediment. Indol is 

 formed, and nitrates are reduced to nitrites. Milk becomes slightly acid. 



(b) Large slightly motile rods, from 1*5-5 fx long, with many 

 peritrichous flagella, staining irregularly by Gram. Oval spores often 

 reniform were noted. Glucose-gelatin plates show circular, white, liquefied 

 areas. On saccharose-potato-agar streak, a broad raised translucent white 

 slime was formed. Grown in broth, the medium remained clear, pro- 

 ducing flocculent deposit, and slight surface ring. Indol reaction was 

 obtained ; nitrates were not reduced to nitrites. Milk was slowly 

 peptonised with the production of acid. 



Oligodynamic Action of Copper Foil on Intestinal Bacteria. $ — H. 

 Kraemer finds from his own experiments and the results of other 

 observers that the presence of metallic copper in water destroys B. coli 

 communis and B. typhosus. The toxicity is due to copper in a crystalloid 

 form ; and when copper foil is placed in distilled water, sufficient copper 

 is dissolved in 1-5 minutes to kill bacteria within 2 hours. 



The toxicity may be lost or neutralised by various substances, and 

 the oligodynamic action depends on temperature. The effects of oligo- 

 dynamic copper on the purification of drinking water are much the same 

 as filtration, except that B. typhosus and B.coli are completely destroyed. 



* Proc. Linn. Soc, N.S.W., 1905, p. 136. t Tom. cit., p. 161. 



t Proc. Amer. Phil. Soc., xlix. (1905) pp. 51-65. 



Dec. 20th, 1905 3 d 



