He was eagerly seeking the means of judging how his laboratory tests would work in practice. He spent some time at Tantonville, in Lorraine, visiting an immense brewery, of which the owners were the brothers Tourtel. Though very carefully kept, the brewery was yet not quite clean enough to satisfy him. It is true that he was more than difficult to please in that respect; a small detail of his everyday life revealed this constant preoccupation. He never used a plate or a glass without examining them minutely and wiping them carefully; no microscopic speck of dust escaped his short-sighted eyes. Whether at home or with strangers he invariably went through this preliminary exercise, in spite of the anxious astonishment of his hostess, who usually feared that some negligence had occurred, until Pasteur, noticing her slight dismay, assured her that this was but an inveterate scientist’s habit. If he carried such minute care into daily life, we can imagine how strict was his examination of scientific things and of brewery tanks. After those studies at Tantonville with his curator, M. Grenet, Pasteur laid down three great principles-- 1. Every alteration either of the wort or of the beer itself depends on the development of micro-organisms which are ferments of diseases. 2. These germs of ferments are brought by the air, by the ingredients, or by the apparatus used in breweries. 3. Whenever beer contains no living germs it is unalterable. When once those principles were formulated and proved they were to triumph over all professional uncertainties. And in the same way that wines could be preserved from various causes of alteration by heating, bottled beer could escape the development of disease ferments by being brought to a temperature of 50° to 55°. The application of this process gave rise to the new word “_pasteurized_” beer, a neologism which soon became current in technical language. Pasteur foresaw the distant consequences of these studies, and wrote in his book on beer-- “When we see beer and wine subjected to deep alterations because they have given refuge to micro-organisms invisibly introduced and now swarming within them, it is impossible not to be pursued by the thought that similar facts may, _must_, take place in animals and in man. But if we are inclined to believe that it is so because we think it likely and possible, let us endeavour to remember, before we affirm it, that the greatest disorder of the mind is to allow the will to direct the belief.” This shows us once more the strange duality of this inspired man, who associated in his person the faith of an apostle with the inquiring patience of a scientist. He was often disturbed by tiresome discussions from the researches to which he would gladly have given his whole time. The heterogenists had not surrendered; they would not admit that alterable organic liquids could be indefinitely preserved from putrefaction and fermentation when in contact with air freed from dusts.