steadily at the rate of about an ounce a day whether the body is active or inactive; this means that the wastage is a matter of the basic metabolism and not of the functional metabolism. The former goes on all the time day and night, in sleep and in waking, and in connection with it the living protoplasm shows this small amount of wastage. Functional metabolism does not, at least under ordinary conditions, increase the amount. Speaking of the body as though it were a machine, we would say that it rusts out just as fast as it wears out. This is one of the features in which the living machine differs from most mechanical devices of human manufacture. Although the loss of protein due to wastage is only about an ounce a day, nobody can get along on a diet which contains no more than that amount. Between three and four ounces of protein is the average daily consumption of adults in this country. We should not forget that our diet consists of meat, bread, vegetables, fruits, etc., which are mixtures of proteins with the other food materials and with a large percentage of water, so that in order to get three or four ounces of protein we have to eat four or five times that weight of ordinary foodstuffs. There has been much debate as to whether it is necessary or even desirable for adults to eat three or four times as much protein as the body requires for making up its wastage. The decision will have to rest in part on what use the body makes of the surplus. Since from time immemorial human beings have habitually eaten every day this large surplus, it is evident that they have been wasting enormous amounts of good food or else that some use is made of it even though it does not serve its purpose of repairing the body waste. The surplus materials are present in the body in the form of amino acids, since what the cells do in repairing their wastage is to take up from the whole quantity of amino acids in the tissue fluids as much as they require for making good their loss. The mixture of amino acids that is left over will make perfectly good fuel provided the nitrogen that is in it is gotten rid of, and this is what happens in the body. All the amino acids in excess of the amount needed for restoring the tissues are decomposed in such a way that the nitrogen is abstracted in the form of ammonia and the substance that is left, which is a starchlike compound, joins with the other starch products and fats to be burned in the body as a source of energy. We do not know certainly which tissues have the power of decomposing the surplus amino acids. At the present time it is believed that all or nearly all of them can do it, so that as they take up from the tissue fluids the particular amino acids which they need for making good their own wastage they take up also the surplus which they decompose, utilizing the starchlike part for fuel and turning the ammonia back into the body fluid as a waste product.