STUDIES ON FERMENTATION, 21 



search many fields of the microscope to discover their existence. 

 Those which we found after the heating must have existed in 

 the beer before that operation ; the heat had destroyed them, 

 without sensibly altering their shape or size ; they could neither 

 multiply nor continue to exert any influence upon the compo- 

 nents of the beer.* 



From these experiments we may easily perceive, on the one 

 hand, that beers apparently sound to the taste do not contain 

 these or any other filiform ferments, save in a scarcely appreci- 

 able quantity ; and, on the other hand, that these same ferments 

 appear with the first unfavourable change in the quality of the 

 beers, and that they exist more or less abundantly in propor- 

 tion to the intensity of disease. 



In certain extremely rare cases it may happen — so, at least, 

 we have been assured, but we have not proved the fact ourselves 

 — that beer may keep sound in bottle, even without the prelimi- 

 nary heating. This exception can only occur in the case of 

 certain beers of a peculiar composition, which are highly 

 hopped, and are made during the favourable months of Novem- 

 ber or December, out of the choicest materials, and fermented 

 with yeast that happens to be pure. In the deposit of such beer, 

 even after a lapse of several months or several years, we should 

 find only the ordinary alcoholic ferment, the slow action of 

 which would merely cause a gradual increase in the quantity 

 of alcohol existing in the beer, and a diminution in the propor- 

 tion of dextrine. This beer might grow old, as wine does, and 

 remain perfectly sound. 



Very often the whole work of the brewer is jeopardized by 

 the unsuspected presence of diseased ferments, a remedy for 



* As the deposit in the heated bottles is, as a rule, inconsiderable, it is 

 necessary to exercise some precaution in collecting it. The bottles are 

 taken up ; after some days' rest they are decanted very carefully, -with 

 as little shaking as possible, until not more than one or two cubic centi- 

 metres (about a tea-spoonful) of the liquid remains at the bottom. The 

 bottles are then shaken vigorously, with the object of collecting the 

 whole of the deposit from the bottom and the sides into this small quantity 

 of liquid ; a drop of this is then examined under the microscope. 



