PLATE IV. 



From " Pasteur's Studies on Fermentation." Macmillan Sf Co., London, 1879. 



"The engraving represents the different diseased ferments, together 

 with some cells of alcoholic yeast, to show the relative size of these 

 organisms." 



Fig. 1 represents the ferments of turned beer, as it is called. These 

 are filaments, simple or articulated into chains of different size, and having 

 a diameter of about the thousandth part of a millimetre (about ^ i o oo 

 inch). Under a very high power they are seen to be composed of many 

 series of shorter filaments, immovable in their articulations, which are 

 scarcely visible. 



In No. 2 are given the lactic ferments of wort and beer. These are 

 small, fine, and contracted in their middle. They are generally detached, 

 but sometimes occur in chains of two or three. Their diameter is a little 

 greater than that of No. 1. 



In No. 3 are given the ferments of putrid wort or beer. These are 

 mobile filaments, whose movements are more or less rapid, according to 

 the temperature. Their diameter varies, but is for the most part greater 

 than that of the filaments of Nos. 1 and 2. They generally appear at the 

 commencement of fermentation, when it is slow, and are almost invari- 

 ably the results of very defective working. 



In No. 4 are given the ferments of viscous wort, and those of ropy 

 beer, which the French csdl Jilante. They form chaplets of nearly spher- 

 ical grains. These ferments rarely occur in wort, still less frequently in 

 beer. 



No. 5 represents the ferments of pungent, sour beer, which possesses an 

 acetic odor. These ferments occur in the shape of chaplets, and consist 

 of the mi/coderma aceti, which bears a close resemblance to lactic ferments 

 (No. 2), especially in the early stages of development. Their physiolog- 

 ical functions are widely different, in spite of this similarity. 



The ferments given in No. 7 characterize beer of a peculiar acidity, 

 which reminds one more or less of unripe, acid fruit, with an odor sui generis. 

 These ferments occur in the form of grains which resemble little spheri- 

 cal points, placed two together or forming squares. They are generally 

 found with the filaments of No. 1, and are more to be feared than the 

 latter, which cause no very great deterioration in the quality of beer, 

 when alone. When No. 7 is present, by itself or with No. 1, the beer ac- 

 quires a sour taste and smell that render it detestable. We have met 

 with this ferment existing in beer unaccompanied by other ferments, and 

 have been convinced of its fatal effects. 



No. 6 represents one of the deposits belonging to wort. This must 

 not be confounded with the deposits of diseased ferments. The latter 

 are always visibly organized, whilst the former is shapeless, although it 

 would not always be easy to decide between the two characters, if sev- 

 eral samples of both descriptions were not present. This shapeless de- 

 posit interferes with wort during its cooling. It is generally absent 

 from beer, because it remains in the backs or on the coolers, or it may 

 get entangled in the yeast during fermentation, and disappear with 

 it. Among the shapeless granules of No. 6 may be discerned little 

 spheres of different sizes and perfect regularity. These are balls of 

 resinous and coloring matter that are frequently found in old beer at the 

 bottom of bottles and casks. They resemble organized products, but 

 are nothing of the kind. 



