178 BACILLUS SUBTILIS AND ITS CONGENERS. 



succinicus. This microbe was discovered by P. FRANKLAND and 

 W. FREW (II.) in a solution of ammonio-ferric citrate, which, 

 originally intended for photographic purposes, was found to have 

 spontaneously fermented with vigour. These observers give the 

 following equation as a deduction from their experiments : 



3C 6 H 14 6 = 4C 2 H 6 + 2CH 2 O 2 + C 2 H 4 2 + C 4 H 6 O 4 + 2C0 2 + 2 H 2 

 ; Dulcite, Ethyl Formic Acetic Succinic Carbon Hydro- 



Mannite. alcohol. acid. acid. acid. dioxide. gen. | 



Many other bacteria also produce ethyl alcohol, but only one 

 more will be noticed, and that a pathogenic organism, viz., Fried- 

 lander's Bacillus pneumonia. According to the researches of 

 F. BRIEGER (I.), and of P. FRANKLAND, STANLEY, and FRE"W (I.), 

 this bacillus, when grown in nutrient solutions containing sugar 

 (saccharose, glucose, mannite), produces ethyl alcohol and acetic 

 acid, together with other fermentation products in smaller amount. 

 These four examples may suffice to support the assertion made 

 above, that ethyl alcohol is producible by bacterial activity. No 

 practical application of this is made in the arts, the higher fungi 

 known as "yeasts" being exclusively used; consequently this 

 property of many Schizomycetes will not be referred to again. We 

 will now supplement the account given of the hay- and potato- 

 bacilli by a few remarks on the 



112. Bacterial Content of the Soil. 



To determine this quantitatively the procedure followed is to 

 finely divide a weighed quantity of soil in sterilised water and 

 then prepare cultures from the washings in the usual manner. 

 P. MIQUEL (IV.), to whom we are indebted for the first determina- 

 tions made in this connection, fixed the unit of weight to be taken 

 as one gram, and it is to this unit that all the subjoined data 

 refer. 



It would, from the first, be expected that layers of the same 

 soil at different depths would exhibit differences, both quantitatively 

 and qualitatively, with regard to their bacterial inhabitants. The 

 property of soils (especially clays) of combining with the fertilising 

 materials supplied in manures, prevents these substances from 

 penetrating in any quantity to great depths, and from this circum- 

 stance alone one would expect the number of bacteria in the sub- 

 soil, at considerable depths below the surface, to be but small. 

 The filtering action of the upper layers of the soil also conduces 

 to the same end, these layers fixing not only the fertilising sub- 

 stances, but also (and that in a purely mechanical way) the bac- 

 teria applied to the soil in manures. Thus it happens that subsoil 

 water is perfectly free from, or at least very poor in, bacteria ; 

 a fact established by PASTEUR and JOUBERT (I.), and of which 



