238 ECONOMIC MYCOLOGY. 



The chemical process of mitrition in fungusea is not the same as in 

 other vef^etables. Fuuffiises do not convert inorganic matter into organic 

 compounds. The}' possess a \'ital force capable of overcoming the natural 

 play of chemical affinities, and they live by appropriating the constituents 

 of the compounds they are thus enabled to decompose. Fermentation ia 

 nothing more than the manifestation of this process of decomposition. 

 Such fermentations as are not produced by the immediate action of living 

 cells are called indirect. They are caused by the intervention of nitro- 

 genous soluble matters elaborated by Uving cells. These soluble fennents 

 are often stored up till circumstances require theii* alterative action. It 

 would seem that most organic substances are subject to fermentative 

 changes, often occasioned by a special ferment plant. There are other 

 ferment plants besides those that are recognised as funguses. Sugaar 

 undergoes several direct fermentations — the alcoholic, lactic, vinous, and 

 butyric. Alcohol by fermentation becomes acetic acid ; albuminous 

 matters and urea are transformed into ammonia by processes of 

 fennentation. 



It will be interesting to sanitarians to know that there is reason for 

 beheving that the conversion of ammonia into nitric acid is caused by the 

 presence of a fungus ; this process has been called nitrification. It goea 

 on constantly in soil that is saturated with decomposing animal matter. 

 The saltpetre of commerce is for the most part imported from India, 

 and is obtained by washing it out of the soil. Nitrification has long been 

 known and carried on artificially. Pasteur suggested that it might be a 

 fennentative change, and some recent experiments show that he was 

 probably correct. MM. Muntz and Schhessing passed sewage water 

 through a porous medium ; for eight days there was no change in the 

 amount of ammonia, but after that time ammonia disappeared and nitric 

 acid took its place. This experiment is only explicable by supposing that 

 germs of a ferment plant were present and took time to mature. This 

 notion was confirmed by another experiment, which proved that the 

 presence of antisei)tic vapours suspended the action. 



Among fermentations the alcoholic takes the first rank; it is the 

 most famihar and the most easily studied. There has been considerable 

 difference of opinion as to the nature of the plant which causes this 

 fermentation. Most English authorities have considered till lately that 

 it was a modified gi'owth of a cominon mould called Pcnicilliiim. Gennan 

 mycologists make it into a genus belonging to the class l\)nil(C among 

 funguses. They call the genus Saccharomyces, and include within it 

 several species. 



Common yeast is Saccharomijccst ccrcvisia ; the composition bakers 

 use has vei-y small cells and is called S. minor. The yeast that grows on 

 malt liquor when left to spontaneous fenncntation, as is the practice in 

 Belgium, is S. aj^iculatuit. Other species appear on musts of wines, and 

 juices of stone fruit. The species that is so important in this district, 

 because it effects the transfonnation of apple juice into cider, appears 

 under the microscope to be identical with that which is found on malt 

 liquor, viz., S. apiculntm. Pasteur has proved by a simple experiment 

 that germs or spoi'is of Sdccluii-onniiu:': exist on the surface of trnipes. Ho 



