It is an absolute fact that in those who are addicted to a diet of carbohydrates, intestinal putrefaction is diminished, owing to the formation of lactic acid from the fermentation of the milk-sugar which is contained in such carbohydrates. Intestinal putrefaction is enhanced by the alkaline contents of the intestines; it can, therefore, be checked by various agencies that diminish the alkalinity of the intestine, such, for instance, as by lactic acid, just referred to. Fatty and acetic acids also effect this; likewise fatty food, which promotes the formation of fatty acids. Cheese may produce fatty and also lactic acids; wherefore it is of value to combat putrefaction in the intestines. Of the further benefits of cheese as an article of food, we make mention in the chapter on the hygiene of food; we also state there that it is unsuitable in those cases in which the intestines are not in thorough order. Great care should be exercised in the quality of the food. The freshness of various foods is of the greatest importance to the intestines, since the main function of the stomach is principally a mechanical one, serving to reduce the food into a convenient form and carry it to the intestines, ready to be there prepared, through the influence of the intestinal juices, into a condition fit for absorption and assimilation. During this process the food is being reduced to its simpler elements, and the more noxious substances are being freed to commence their baneful activity. These substances first of all create an inflamed condition of the intestines; then, being absorbed into the blood, they cause a general intoxication. Fortunately they are not frequently absorbed, and thus their injurious effect is limited to the intestine. Among other such injurious foods we may mention fish and oysters, sausages and meats that are in a state of decomposition; fruit that is unripe or unsound; and canned food in which certain drugs are used as preservatives, such being poisonous in varying degree, examples being salicylic boracic, and sulphuric acids, etc., and at times even the terrible poison, verdigris. Fresh food should always be preferred to canned food, or to food preserved in other forms for too long a period (see also chapter on the hygiene of food). The stomach, and intestines also, can frequently suffer damage from ice cold drinks, especially if taken habitually and in large quantities. As already mentioned in the chapter on the hygiene of the kidneys, we should never forget that every sort of food or drink must pass a series of delicate epithelia of our noblest organs, which can be injured by sharp and poisonous substances with which they come in contact.