The mineral salts which are taken into the body are dissolved by all the digestive fluids which we have named, some by the saliva and the juices of the intestinal tube, and others, which require acids for their solution, by the gastric juice. Nearly all these digestive fluids are also powerful antiseptics and are able to destroy germs when the health of the body as a whole is good. The gastric juice, for instance, acts as an antiseptic, preserving the stomach contents from putrefaction during the digestive process. It is a remarkable fact that the gastric juice, although it is so essential to life, is a deadly poison, which, when introduced into the blood produces insensibility and death. These digestive juices and organs are able completely to dispose of all the food elements which are introduced into the body, save proteid alone. The sugars and starches are either completely absorbed and oxidized, or stored up in the form of surplus fat. The oxidation or burning up of proteid, however, is never complete. There is always a certain amount of unburnable substance left behind from the processes of metabolism, which the liver and kidneys of the body have to dispose of. If only as much proteid as is needed by the body for the upbuilding of its tissue, and the repair of waste, is taken, the body can very readily handle it; but an excess of proteid is highly disadvantageous. Professor Chittenden, in his great work, “The Nutrition of Man,” has set forth in elaborate detail the process of the assimilation of proteid. It appears that there are many kinds of proteid; the proteid of eggs is different from that of meat, and that again from the proteid of beans, and so on; and human proteid is different from all. Consequently, the body is obliged to transform every kind of proteid which is brought to it. This proteid is then absorbed by the blood, and carried to the tissues, which are kept perpetually bathed in a supply of nutritive material. The taking of more proteid than is needed would not be so dangerous if it were simply passed on without being digested; nor even if it were digested and transformed, and then promptly eliminated. But what actually happens is that the new proteid taken in is passed through all the stages of assimilation, and drives out in front of it, so to speak, the proteid which has already been prepared, but has not yet been used. And the result is, of course, to throw a double strain upon the liver and the kidneys, the organs of elimination.