As lactic fermentation serves so well to arrest putrefaction in general, why should it not be used for the same purpose within the digestive tube?
It is a matter of common knowledge that putrefaction and butyric fermentation are arrested in the presence of sugar. Whereas meat preserved without special care soon putrefies, milk in exactly the same conditions does not putrefy, but becomes sour, the reason being that meat is poor in sugar whereas milk contains a good deal of it. However, the scientific explanation of this fundamental fact is difficult. It has been shown conclusively that sugar itself cannot prevent putrefaction. Milk, for instance, however rich in sugar it may be, readily putrefies in certain conditions. Sugar preserves organic matter from putrefaction only because it can readily undergo lactic fermentation, and this fermentation is the work of the microbes described fifty years ago by Pasteur. That great discovery proved the part played by microbes in fermentation and founded bacteriology, a science equally rich in theory and in practice.
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.
Dr. Pochon, assistant to Professor Combe[134] at Lausanne, has repeated on himself the experiments of Cohendy. He took for several weeks milk curdled with pure cultures of lactic acid microbes and obtained “results that were quite definite as to intestinal putrefaction.” Analysis of his urine showed that there was a marked diminution of indol and phenol, substances which are certain indexes of intestinal putrefaction.
In addition to such observations on lactic bacilli there is a good deal of knowledge as to the effect of lactic acid taken in bulk. The result of the various observations[135] shows that the acid lessens intestinal putrefaction and lowers the quantity of sulpho-conjugate ethers in the urine. This fact explains why favourable results follow the use of lactic acid in many intestinal diseases such as infantile diarrhœa, tuberculous enteritis and even Asiatic cholera. The addition of this remedy to practical therapeutics is due chiefly to Professor Hayem. It is employed not only in the treatment of diseases of the digestive system (dyspepsia, enteritis and colitis), but is indicated also in diabetes and is used locally in tuberculous ulcerations of the larynx. As quantities up to twelve grams can be given by the mouth daily, it is plain that the system is tolerant of this acid. It is either oxidised in the tissues or excreted with the urine. In the case of a diabetic woman who had taken 80 grams of lactic acid in four days, Nencki and Sieber[136] found no traces of it in the urine. On the other hand, Stadelmann[137] found a notable quantity of the acid in another diabetic patient who had been taking over four grams daily.