I need not pause to develop the theme that the anti-putrescent action of the lactic fermentation depends on the production of lactic acid by microbes, because I have explained the matter at length in the tenth chapter of the “Nature of Man.” If the lactic acid be neutralised, the organic matter soon putrefies, notwithstanding the presence of the lactic microbes. The most important point is as to whether lactic fermentation really arrests intestinal putrefaction. Several sets of observations have been made upon this matter. Dr. Herter,[132] of New York, injected directly into the small intestine of a number of dogs quantities of different microbes. To test the action of these on intestinal putrefaction, he investigated the sulpho-conjugate ethers in the urine, as he believed, in accordance with current and well justified opinion, that these substances are the best proofs of the existence of putrefaction. He found that whilst the introduction of quantities of _Bacillus coli_ or _Bacillus proteus_ increased the intestinal putrefaction, lactic bacilli notably lessened it. Herter found a notable diminution of sulpho-conjugate ethers in the urine of dogs which had been treated with the lactic microbes. The experiments which Dr. M. Cohendy[133] performed upon himself during a period of nearly six months are still more interesting. When Dr. Cohendy had proved that much intestinal putrefaction occurred during a period of 25 days, in which he lived on an ordinary mixed diet, he began to take pure cultures of lactic bacillus, taken from yahourth. In a period of 74 days, he took quantities varying from 280 to 350 grams of the culture. Analysis of the urine during the progress of the experiment showed that intestinal putrefaction had notably decreased whilst the lactic bacilli were being taken, and that the diminution persisted seven weeks after the taking of the bacilli ceased. Dr. Cohendy gives it as the direct result of his experiment that the introduction of lactic ferment into the intestine definitely arrests putrefaction. He obtained this result on a diet consisting of 400 grams of soup, 150 of meat, 700 of grain-food, 400 of green vegetables, 300 of fruits and dessert and a litre of water. He came to the conclusion that the elimination of meat from the diet was unnecessary, as the particular kind of lactic ferment he employed was extremely active in inhibiting the proteolytic ferments. Later experiments made by Dr. Cohendy showed that the lactic bacillus became so acclimatised in the human intestine that it was to be found there several weeks after it had been swallowed.