[Sidenote: Proper feeding chief factor in reducing bacterial growth] We do not need, however, to seek for any one specific remedy against intestinal decomposition, but should study the selections, combinations, and proportions of our food at each meal with the view of reducing to the minimum the growth in the alimentary tract. DIGESTIVE EXPERIMENTS It is well known that only a portion of the food taken into the alimentary canal is digested and absorbed into the circulation. It is obvious that the undigested food plays no part in the process of metabolism, therefore it is necessary to know the amount of the various food elements that are digested. For this reason we will notice briefly the method used in making digestive experiments. [Sidenote: Determination of the amount of food the body uses] The food eaten for a certain period of time is analyzed and weighed, and the intestinal excreta, corresponding to the quantity of food under study, is also weighed and chemically analyzed. The difference should show the amount of food actually digested. There are several serious difficulties in the way of making accurate digestive experiments: [Sidenote: Quantity of feces and time consumed in passing food through the body] 1. It is very difficult to determine the quantity of feces (intestinal excreta) that corresponds to a given quantity of food. A digestive experiment is usually conducted for a period of about one week, the man or animal being given a spoonful of lampblack at the beginning and at the close of the experiment. The lampblack being a finely powdered form of pure carbon, is insoluble in the digestive juices, hence passes through the body without change, thus blackening or marking the feces at the beginning and at the end of the test period. The subject under experiment should be given the same diet for a few days before and after the experiment, so that the error due to the inability to accurately separate the feces will be reduced to a minimum. [Sidenote: Measuring the digestible portion of food] 2. The digestive juices, and especially the bile, pour considerable material into the alimentary canal which cannot be distinguished from the undigested elements of food. However, it is fair to assume that when large quantities of body-proteids are poured into the alimentary canal, and passed out with the feces, this amount of matter is wasted by the body, hence should be charged against the food which stimulated the secretion. For example: If grain causes a large secretion of digestive enzyms, it is no more than fair to say that grain is less digestible than milk, which wastes less body-matter in its digestion. [Sidenote: Certain foods may either aid or hinder digestion] [Sidenote: The mono-diet system]