The manifold functions of the intestine create many practical problems for the physician. Not the least of these is the fact that the intestine is not sterile; probably the first swallow of food of the newborn infects the tract. The observation that the clotting time of the blood is reestablished at the normal level ordinarily within a week indicates that the intestinal bacterial activity involved in the synthesis of vitamin K is active at that time. Through this symbiotic activity, no doubt, the organism as a whole reaps benefits of various kinds from the biochemical reactions in the intestine. Vigorous support for this thesis has been adduced by some recent observations of synthetic activity in ruminants.
Although micro-organisms can flourish on nutrient mediums whose nitrogen is provided by such simple organic compounds as asparagin, succinamide and urea, only amino acid nitrogen, either as such or in the form of protein,