A special case in which the hyaline layer is slightly attacked and its brilliance destroyed has been described by Eitner.[153] A slimy film was formed on the surface of the drench and also on the grain of the skins. This film was found to consist of Bacillus megaterium (the potato bacillus), and where it was growing on the hyaline layer the latter was etched as it were, by the peptonizing enzyme secreted by the bacillus, so that when tanned the grain was covered with dull patches very much resembling “blast.” [153] Der Gerber, 1898, p. 204. *Fermentations in the Drench.*--Compared with the dung bate, or puer, the fermentation taking place in the bran drench is a simple one; as will be shown in detail in the next chapter, about half the weight of the bran consists of starch; this becomes hydrolysed by the enzymes in the bran (and in some cases secreted by the bacteria) into glucoses. According to the following equation:-- (C_{6}H_{10}O_{5})_{n} + H_{2}O = n C_{6}H_{12}O_{6} starch glucose This expresses the change in its simplest form; in reality it is much more complex, various dextrins and sugars being formed simultaneously. The sugars are then fermented by a variety of bacteria with formation of various organic acids, in accordance with the equation C_{6}H_{12}O_{6} = 2 CH_{3}CH(OH)COOH which represents the formation of lactic acid. In addition, formic and butyric acids are produced along with small quantities of other bodies, as will be shown. It is pretty certain that the butyric acid is formed by the further fermentation of the lactic acid and lactic salts in the liquid; at the same time CO_{2} and hydrogen are evolved as follows:-- 2 C_{3}H_{6}O_{3} = C_{4}H_{8}O_{2} + 2 CO_{2} + H_{2} [Illustration: Fig. 27.--Organisms in Bran Drench × 1000.] Fig. 27 is a drawing of the organisms seen in the drench, under a magnification of 1000 diameters. This was taken from a drench which had been set about 3 hours, and was just beginning to ferment; the bacteria form chains of varying length: the short chains have a slow motion in the liquor. As the fermentation proceeds, these form longer chains (Fig. 28), some of which are very beautiful objects, especially when viewed by dark ground illumination. The other organisms present are bacteria and bacilli from the puer, and at a later stage, as the nutrient material for the bran ferment becomes less, they begin to develop, first causing butyric and finally putrefactive fermentation. [Illustration: Fig. 28.--Chains of Bran Bacteria × 1000.] [Illustration: Fig. 29.--Bran Fermentation. Advanced Stage.]