urine; those which produce marsh gas by the fermentation of cellulose; those which effect the decomposition of albumin, with an evolution of hydrosulphuric acid; those which give rise to the putrefactive decomposition of organic material, the number of which is very large; the bacteria in the soil which reduce nitrates with liberation of ammonia and free nitrogen, and those which oxidize ammonia. The study of these bacterial ferments is still being vigorously prosecuted, and practical results of importance in agriculture and the arts have already been attained. In the future we may look for numerous additions to these practical applications of our knowledge. The use of pure cultures for producing useful fermentations must give the best result with the least liability to loss of material from the presence of undesirable species. It is known that the flavor of butter and of different kinds of cheese is due to various bacterial ferments, and there is good reason to suppose that a better product and greater uniformity would be attained by the use of pure cultures of the species upon which special flavors depend. I understand that in this country quite a number of dairies are now using pure cultures of a certain bacillus (Bacillus 41 of Conn) for giving flavor to their product. It is probable that similar methods will soon be introduced in the cheese-making industry. A recent English publication, which I have not yet seen, is entitled Bread, Bakehouses, and Bacteria. It will, no doubt, be found to contain information of practical value to those engaged in breadmaking.
Pasteur's studies relating to the micro-organisms causing abnormal and injurious fermentations in wine, the results of which he published in 1866 (Études sur le Vin, ses Maladies, etc.), have resulted in an enormous saving to the wine-making industry in France and other countries where wine is produced upon a large scale; and his investigations relating to the cause and prevention of the infectious diseases of the silkworm, which threatened to destroy the silk industry in France, have resulted in even greater benefits to the material interests of his country and of the Vv'orld (published in 1870).
Agricultural chemists predict that in the near future cultures of the nitrifying bacteria of the soil will be made on a large scale for the use of farmers, who will add them to manures for the purpose of fixing the ammonia or perhaps will distribute them directly upon the soil. Should this prove to be a successful and economic procedure, the extent of the interests involved will make it a "practical result" of the first importance. Another application of our recently acquired knowledge which has already proved useful to farmers in certain parts of Europe relates to the destruction of field mice by distributing in the grain fields bread
