Two kinds are recognized, "high" 

 and " low " yeast, the former rising 

 to the top of the liquid during 

 fermentation and the latter form- 

 ing a sediment in the vats. High 

 yeast is the one used in English ale 

 fermentation, low yeast producing 

 the lighter lager beer. 



(2) Saccharomyces ellipsoideus is 

 the ordinary ferment of vinous 

 fermentation by which " must " 

 or grape juice is converted into 

 wine. (3) Saccharomyces pastorianus 

 also occurs in wine-making, and 

 when present during brewing gives 

 a bitter taste to the beer. 



(4) Saccharomyces mycoderma is 

 the cause of " mother " which ap- 

 pears on the surface of wine or beer 

 after exposure for some days to 

 the air. 



Hansen, the Danish brewing 

 chemist, has isolated and culti- 

 vated two pure yeasts, species of 

 Saccharomyces cerevisiae, by using 

 which it is possible to obtain beers 

 of distinctive properties. 



ACETIC FERMENTATION. It has 

 long been Jjiown that when wine 

 is exposed to the air it sours turns 

 into vinegar and the manufacture 

 of vinegar wort is an old-established 

 art. It is essentially an oxidation 

 process, and Pasteur first detected 

 the organism, " flowers of vinegar," 

 Bacillus aceti, which effects the 

 change. Hansen has detected two 

 distinct -species with the same 

 properties. Both require oxygen 

 for their growth, which is most 

 favoured by a temperature of 33 C. 



Lactic fermentation produces 

 sour milk. The milk sugar is first 

 split up into lacto-glucose and then 

 into lactic acid by the agency of 

 Bacillus acidi lactici. A special 

 bacillus, named Bacillus Caucasi- 

 cum, was found by Mechnikoff to 

 be present in the soured milk 

 employed as a beverage under the 

 name " yoghourt." 



Viscous fermentation, due to 

 Pediococcus cerevisiae, is the cause 

 of " ropiness " in brewing, and a 

 similar condition in bread-making. 



Nitrification in Agriculture 



Nitrification or the oxidation of 

 ammonia into nitrous and nitric 

 acids takes place through the 

 agency of bacteria. Warington's 

 investigations at Rothamsted have 

 shown the importance of nitri- 

 fication hi agriculture. Recently 

 special preparations of nitrification 

 bacteria have been employed com- 

 mercially in promoting the growth 

 of leguminous plants. 



Enzymes or soluble ferments 

 may be defined as substances pro- 

 duced by living plants or animals, 

 and capable of acting catalytically 

 on contiguous compounds. They 

 are thus classified : 



31 20 



Amylolytic, which convert starch 

 paste into soluble starch and 

 soluble starch into maltose and 

 dextrose. To this class belong 

 diastase, derived from malt ; ptya- 

 lin, from saliva ; and amylopsin, 

 from pancreatic juice. Cellulolytic, 

 represented by cytase ; this is de- 

 rived from green malt, which dis- 

 solves the cellulose walls of grain. 

 Coagulative, such as fibrin-ferment 

 from blood, myosin-ferment from 

 muscle, and rennet from gastric 

 juice, which coagulate protein mat- 

 ter. Emulsive, which convert 

 glucosides into glucose and other 

 compounds. Examples are ermil- 

 sin, obtained from almonds, and 

 myrosin, from mustard Inver- 

 sive, such as invertase from yeast 

 and invertin from intestinal juice, 

 which convert sucrose into glucose, 

 and maltase from yeast, which 

 changes maltose into glucose. 

 Enzymes in Industry 



Proteolytic enzymes convert 

 proteins into peptones. Examples 

 are pepsin from gastric -juice, 

 trypsin from pancreatic juice and 

 papain from Carica papaya. Steato- 

 lytic enzymes, of which steapsin 

 of the pancreatic -juice is an ex- 

 ample, separate fats into fatty 

 acids and glycerin. Zymase ob- 

 tained from yeast converts sugar 

 into alcohol and carbon dioxide. 



Enzymes play a considerable 

 part in several important indus- 

 tries, such as brewing and leather 

 making. In the preparation of 

 rubber, the drying of tea, and the 

 curing of tobacco the proper treat- 

 ment of the vegetable enzymes 

 contained in these substances de- 

 termines the quality of the pro- 

 ducts. In drying drugs the 

 activity often depends upon the 

 prompt killing by heat of the 

 enzymes in the plants. Special 

 processes have been evolved in 

 which the vapour of boiling alcohol 

 is employed for this purpose. 



Putrefaction is the process of 

 fermentation of nitrogenous or- 

 ganic matter, especially albu- 

 minoids, accompanied by the pro- 

 duction of evil -smelling gases. 

 The process is due to micro- 

 organisms, the decomposing sub- 

 stances yielding, among other 

 organic bases, methylamine, tri- 

 methylamine, and the important 

 bodies known as ptomaines. Many 

 of the ptomaines are very poison- 

 ous. They are produced readily in 

 decaying meat and fish, and when 

 introduced into the human body 

 give rise to very serious blood 

 poisoning. See Brewing; Distilling: 

 Liebig ; Pasteur ; Sterilization. 



Fermo (anc. Firmum Pice- 

 num). City of Italy, in the prov. 

 of Aucoli Piceno. It stands on an 

 eminence, rather more than 1,000 



FERN 



ft. high, 4 m. from the Adriatic and 

 36 m. by rly. S.E. of Ancona. En- 

 closed by battlemented walls, it 

 contains a 13th century cathedral, 

 a town hall and library, besides 

 remains of Roman buildings. 

 Porto San Giorgio, its port, ex- 

 ports grain, wool, and silk. 

 Fermo was founded by the 

 Romans in 264 B.C., and was a free 

 city from 1199 to 1550, when it fell 

 to the papacy. Pop. 7,000. 



Fermoy. Urban dist. and mar- 

 ket town of co. Cork, Ireland. It 

 stands on the Blackwater, 15 m. 

 E. of Mallow, on the G.S. & W.R. 



Mir 



Fermoy, Ireland, the Roman Catholic 

 church of S. Patrick 



Its importance is chiefly due to 

 the efforts of John Anderson, a 

 Cork merchant, who began to build 

 here in 1791, and later gave a site 

 for the erection of military barracks 

 and founded Fermoy college. The 

 town contains a Roman Catholic 

 cathedral and S. Colman's Roman 

 Catholic college. Salmon and trout 

 fishing is engaged in, and a trade in 

 corn carried on. There is a race- 

 course in the vicinity. Fermoy was 

 the scene of rioting on June 28-29, 

 1920, when the military wrecked 

 a number of buildings as reprisal 

 for the capture of General Lucas. 

 Market day, Sat. Pop. 6,863. 



Fern (Pteridophyta). Most high- 

 ly organized division of the flower- 

 less plants (Cryptogamia ), which are 

 characterised in the main by being 

 built solely of cells. Pteridophytes 

 alone of the cryptogams possess 

 vessels. They are mostly perennial 

 herbs, only a few being annuals. A 

 few others have shrubby roots or 

 woody trunks, e.g. the tree-ferns. 

 Besides the ferns proper, the pteri- 

 dophytes include the horsetails and 

 ?lub-mosses, all agreeing generally 

 in their mode of reproduction. This 

 is known as the Alternation of 

 Generations. As it has been tersely 

 put by a modern writer : " Of four 

 successive generations of fern-life, 



