Recently, at the suggestion of Mr. Fletcher,[126] the advantage of eating extremely slowly has been recognised, the object being to prepare for the utilisation of the food materials, and to prevent intestinal putrefaction. Certainly the habit of eating quickly favours the multiplication of microbes round about the lumps of food which have been swallowed without sufficient mastication. It is quite harmful, however, to chew the food too long, and to swallow it only after it has been kept in the mouth for a considerable time. Too complete a use of the food material causes want of tone in the intestinal wall, from which as much harm may come as from imperfect mastication. In America, where Fletcher’s theory took its origin, there has already been described under the name of “Bradyfagy” a disease arising from the habit of eating too slowly. Dr. Einhorn,[127] a well-known specialist in the diseases of the digestive system, has found that several cases of this disease were rapidly cured when the patients made up their minds to eat more quickly again. Comparative physiology supplies us with arguments against too prolonged mastication. Ruminants, which carry out to the fullest extent Mr. Fletcher’s plan, are notable for extreme intestinal putrefaction and for the short duration of their lives. On the other hand, birds and reptiles, which have a very poor mechanism for breaking up food, enjoy much longer lives. Prolonged mastication, then, cannot be recommended as a preventative of intestinal putrefaction any more than the surgical removal of the large intestine or the disinfection of the digestive tube. The field lies open for other means which may probably solve the problem more completely and more practically. V LACTIC ACID AS INHIBITING INTESTINAL PUTREFACTION The development of the intestinal flora in man—Harmlessness of sterilised food—Means of preventing the putrefaction of food—Lactic fermentation and its anti-putrescent action—Experiments on man and mice—Longevity in races which use soured milk—Comparative study of different soured milks—Properties of the Bulgarian _Bacillus_—Means of preventing intestinal putrefaction with the help of microbes At birth the human intestine is full, but contains no microbes. Microbes very soon appear in it, because the meconium, the contents of the intestines of new-born children, composed of bile and cast-off intestinal mucus cells, is an excellent culture medium for them. In the first hours after birth, microbes begin to reach the intestine. In the first day, before the child has taken any food whatever, there is to be found in the meconium a varied flora, composed of several species of microbes. Under the influence of the mother’s milk this flora is reduced and comes to be composed almost entirely of a special microbe described by M. Tissier and called by him _Bacillus bifidus_.