( 692 ) 



0,05 7o) ^^^'"^^ introduced inlo a thin layer of one of the folloAA^ng 

 (Miliiiiv lifjiiids. wliicli were iiioeulated willi earth: 



Tapwater 100, NH.Cl 0,05, K,ÜP(), 0,05, 

 o, „ n KNO, 0,05, „ 0,05, 



III inv previous cuniiniuiicalioii I lia\ e already poijiled out, that 

 niirilicalioii and denilrification may take place tog-ether in garden 

 soil and that the aeration decides, w iiich of these processes will he 

 the i)redoniinant one; the same conclusion may, therefore, now he 

 drawn for cellulose as a nutrient material. A closer examination 

 however shows, that the two jirocesses cannot occur simulla- 

 neouslv in the same particle, hut that a localisation must take place, 

 in this wav. that strong aeration is necessury in rhe particles Avhere 

 nitriiication >ets in, whilst the exclusion of air is necessary for the 

 (Icnitritication process. 



As has already heen jtreviously ohserved formation of nitrite 

 takes place in the tirst stage of the denitrification j>rocess in the 

 presence of cellulose and as this suhstancc Ity no means ju-events the 

 oxidation of tlic nitrite to nitrate, these two processes, occurring simul- 

 taneouslv, may cause the steady disap|)earance of celhdose. 



We therefore see, that these same |)rocesses may cause the ilisap- 

 [)earance of cellulose in soil and in ^vaters. which [»l;didy shows their 

 great importance in the •'self-piirilication "'. as also in the hiological 

 purilication of scNvage. 



'2. IVic iwrohtc ilrcinn iiosifnni i>f <-i'llnh>sf hij Ixicti'rui. 



In order to demonstrate «lenitrification in the presence of cellulose 

 in the manner descrihed aho\e, a very small quantity of this suh- 

 stancc (al)ont 0,05"/„) oidy niusi he present, for (»n using more 

 say, '2"/„ the nature of the |M-ocess is completely changed. This must 

 he attril)uted to a strong decomposition of the cellulose hy aëro[)ic 

 hacteria, which then takes place and which produces a large quantity 

 of solnhle organic matter, rendering the nitriiication inq)ossihle. This 

 last phenomenon may l>e hest ohserved when use is njade of the 

 following culture medium : 



Tapwater 100, paper 2, NH^Cl 0,1, K,HP(), 0,05,i'halk 2. 



Instead of NH.Cl we may also add KNO, (0,1), KNO, (0,1), peptone 

 (0,1) or an unlimited quantity of MgNH^PO^. The cultivation takes 

 place at 28 — ^35° in Erlknmeijkr flasks in a layer from 0,5 — J cm. 

 in thickness, thus, under very aërohic conditions, so that on usijig 

 KNO.^ or KNO.,, no denitrification can he expected, at least not at 

 the commencement. 



