( 68V) ) 



capable of inducing denitrification, the cottonwool, Iiowevcr, l)eing 

 attacked with great difticnlty. No denitritication could be observed 

 with sa^vdust or turf, whilst Van Sexus (1. c. pg. 104) has also l)een 

 nnable to observe decomposition of wood-cellulose by real anaerobic 

 bacteria. This extraordinary difficult decomposition of wood-cellulose 

 ont of contact with the air, is, according to this investigator, perhaps 

 the key to the explanation of the formation of hunnne substances, 

 peat, browncoal and coal. 



The distribution of the microbes, engaged in the denitritication ni' 

 cellulose, in the mud from canals, seems to l)e a very general one, 

 as each sample emploA^ed contained these germs. Altliough they 

 are also very generally distributed in the earth, their number per 

 cc. appears therein to be less, for, on using earth as infecting material, 

 the action Avas delayed. Even in sea water, taken from the port of 

 den Helder, were ahvays microl)es found, which in the presence ot 

 cellulose could induce denitritication ; in how far these forms are similar 

 to the terrestrial ones has not yet been ascertained, bnt I wish to 

 call particular attention to the fact, tiiat, at least near the shore, 

 cellulose may disappear by denitrification. 



The changes, which cellulose undergoes during this process, 

 are visible to some extent with the naked eye: the white fibres 

 soon turn orange and the pulp acquires a viscous consistency. 

 Microscopically, it appears, that already very soon after inoculation 

 some of the fibres are inclosed in a bacterial mucus and after 

 a prolonged culture this is the case Avitli nearly all the fibres. 

 At first, the whole of the fibre is still xevx i)lainly visible within 

 this mucus, but gradually, on account of the decomposition, it 

 completely disintegrates into loose fibrillae and at last we only 

 tiud a few particles of cellulose left, or the fibre disappears altogether 

 (fig. 1). This destruction of the cellulose becomes very pronounced, 

 when instead of paper-pulp strips of filterpaper are used. Hy 

 repeatedly adding fresh nitrate we then finally obtain bacteria-mem- 

 branes, which still have the exact shape of the strips of paper but 

 in Avhich we only meet isolated fibres disintegrated into tibrillae 

 or even still more decomposed. As is already stated, the woody 

 sul)&tance is not attacked by denitrifying bacteria, the few annulated, 

 spiral and pitted vessels, Avhicli are contained as impurities in the 

 filterpaper, are found unaltered in this mucus. Fig. 2 shows the 

 form of two \erv strongly dissolved paperfibres («) and some 

 non-attacked woody elements (|i, y and rf), wliich are still found in 

 such preparations. 



The gases, liberated during the denitritication of cellulose and of 



