§ I. On the conditions which cause variations in the nature of the organized products existing in infusions 33 § II. Experiments on blood and urine taken in their normal state, and exposed to contact with air that has been deprived of the particles of dust which it generally holds in suspension 40 § III. Experiments on the juice contained in grapes 54 § IV. Wort and must exposed to common air 59 § V. New comparative studies on the germs held in suspension by the air of different places which are near each other, but subjected to different conditions affecting the production and diffusion of the particles of dust found in them 72 § VI. Yeast may become dry and be reduced to dust without losing its faculty of reproduction 81 CHAPTER IV. THE GROWTH OF DIFFERENT ORGANISMS IN A STATE OF PURITY: THEIR AUTONOMY. § I. Growth of _Penicillium glaucum_ and _Aspergillus glaucus_ in a state of purity.—Proofs that these fungoid growths do not become transformed into the alcoholic ferments of beer or wine.—Preliminary inquiry into the cause of fermentation 86 § II. Growth of _Mycoderma vini_ in a state of purity.—Confirmation of our original conjectures as to the cause of fermentation.—_Mycoderma vini_ does not change into yeast, although it may give rise to fermentation 108 § III. Growth of _Mycoderma aceti_ in a state of purity 121 § IV. Growth of _Mucor racemosus_ in a state of purity.—Example of life more active and lasting when removed from the influence of air 127 CHAPTER V. THE ALCOHOLIC FERMENTS. § I. On the origin of ferment 143 § II. On “spontaneous” ferment 182 § III. On “high” and “low” ferments 186 § IV. On the existence and production of other species of ferment 196 § V. On a new race of alcoholic ferments: Aërobian ferments 205 § VI. The purification of commercial yeasts 219 CHAPTER VI. THE PHYSIOLOGICAL THEORY OF FERMENTATION. § I. On the relations existing between oxygen and yeast 235 § II. Fermentation in saccharine fruits immersed in carbonic acid gas 266 § III. Reply to certain critical observations of the German naturalists, Oscar Brefeld and Moritz Traube 279 § IV. Fermentation of dextro-tartrate of lime 284 § V. Another example of life without air.—Fermentation of lactate of lime 292 § VI. Reply to the critical observations of Liebig, published in 1870 316 CHAPTER VII. NEW PROCESS FOR THE MANUFACTURE OF BEER. § I. Preliminary experiments 338 § II. Method of estimating the oxygen held in solution in wort 353 § III. On the quantity of oxygen existing in a state of solution in brewers’ worts 364 § IV. On the combination of oxygen with wort 371 § V. On the influence of oxygen in combination on the clarification of wort 381 § VI. Application of the principles of the new process of brewing with the use of limited quantities of air 387 APPENDIX 396 INDEX 403 INDEX TO PLATES. I. Principal disease-ferments met with in wort and beer 6