ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 235 



after washing out any adherent culture-media and most of the con- 

 stituents soluble in water. 



The acid values of the ether and alcoholic extracts, the total ash and 

 the phosphoric acid, were also determined. 



It is suggested that the virulent human, bovine, horse, and swine 

 tubercle bacilli, which contain less harmless matter than the attenuated 

 human tubercle bacilli, produce greater amounts of poisonous proteids. 



It was previously shown* that cultivations of human tubercle 

 bacilli contain a very virulent acid-like necrotic substance. This, being 

 readily soluble in water, would not be included in the above extracts. 



Decomposition of Cellulose by Aerobic Micro-organisms.t — G. van 



Iterson has studied the decomposition of cellulose by denitrifying 

 bacteria. He experimented with Swedish filter paper and found that 

 the cellulose is broken down by the action of denitrifying, non-spore- 

 forming, aerobic bacteria, provided that there is a limited supply of air. 

 If nitrates be present in the nutritive medium, only nitrogen and 

 carbon dioxide are evolved. 



Amongst the aerobic, non-spore-forming bacteria which attack cellu- 

 lose, the brown pigment bacterium, Bact. ferrugineus, is predominant. 

 A chief cause of the brown colour in humus is a pigment formed by 

 the action of bacteria or moulds on cellulose. The aerobic destruction 

 of cellulose accounts for the fact that wood or rope partly imm ersed in 

 water become weak at the place of contact of water and air. 



* Centralbl.Bakt., l te Abt., Orig., xxii. (1903) pp. i., 209. 



t Proc. K. Akad. Witensch. Amsterdam, v. (1903) pp. 685-703. See also Journ. 

 Ohem. Soc, cceclxxxix. (1903) p. 50o. 



R 2 



