Eitner states that the fermentation is alcoholic at the commencement, and then becomes an acid fermentation with generation of gas. In tan liquors there is no doubt that this is the course of the acetic fermentation, as has been shown by Andreasch,[157] but in the usual type of bran drench the action is certainly a different one. The acetic acid, as far as we can ascertain, is produced directly from the dextrose, without the previous production of alcohol, since the presence of the latter is not shown by tests in any stage of the fermentation.[158] No yeasts were observed[159] and no alcohol was found in any stage of the fermentation.[160] J. O’Sullivan remarks that although it has not been noticed it is possible that in this case the production of alcohol and its oxidation into acetic acid are simultaneous, but that there is no _preliminary_ fermentation by yeasts followed by acetic fermentation by bacteria such as Eitner indicates is certain. [157] Der Gerber, 1895, p. 193, etc. [158] J.S.C.I., 1897, p. 513. [159] Ibid., 1890, p. 28. [160] Ibid., 1893, p. 422. To sum up the conclusions arrived at from the experiments above quoted. The starch of the bran or flour is first transformed into glucoses and dextrin by the action of an unorganized ferment called _cerealin_. The glucoses are then fermented by certain species of bacteria, Bacillus furfuris being perhaps the chief, with the formation of lactic, acetic, formic and butyric acids, and the evolution of carbon dioxide, hydrogen, nitrogen, and a small quantity of sulphuretted hydrogen. The principal acid produced is lactic; the acetic acid is produced directly from the glucoses by the above-mentioned bacteria without any preliminary alcoholic fermentation by yeasts. The mode of action of the drench on the skins may be summed up as follows:-- 1. The solution of the last traces of lime which has not been removed by the bate, by the organic acids produced by the fermentation, and the subsequent swelling action of these on the skin fibres. The acids also dissolve a small amount of skin substance. 2. Simultaneously with (1) the distension and floating of the skins by gases produced by the fermentation, so enabling them better to take up the acids. 3. The mechanical absorption of dirt by the particles of bran or flour in the drench. It is not proposed to enter into further detail, since the next chapter, consisting of the original papers of Dr. W. H. Willcox and the author, contains a pretty complete account of the analysis of the drench and theory of the drenching process. CHAPTER X. ORIGINAL PAPERS ON DRENCHING. 1. FURTHER CONTRIBUTION ON THE NATURE OF BRAN FERMENTATION. By J. T. Wood & W. H. Willcox, B.Sc.(Lond.). (Reprinted from the Journal of the Society of Chemical Industry, May 31, 1893. No. 5, vol. xii. p. 422.)