The question is not yet decided whether, in addition to the derange ment of mineral salt metabolism due to the withdrawal of alkalies, we may not also encounter sometimes a genuine acidosis, brought about by the increase of organic aeid.s in the circulation; the previously mentioned investigations of acidosis in older children make this seem probable.
Even if the condition known as "acid intoxication" has not taken on more definite shape and form as the result of further studies, it led Cgerny and his pupils to a thorough investigation of the que.stion of ammonia excretion and has furnished valuable results from the clinical standpoint. Clinicians soon learned to avoid giving too large amounts of fat, and recognized the great advantages inherent in a diet rich in earbohydrates and low- in fats in certain disturbances of nutrition in infancy. One knowledge of the harm which may result for the healthy, infant in consequence of a diet which is persistently- too rich in fats, is amplified by the recognition of the changes 1Y-hich follow in the metab olism of the mineral salts. Prophylaxis and treatment thus obtain a firm footing. Here wc have at least one example of the harmful results of one form of overfeeding, where light has been thrown on our empiri cism as the result of exact investigation. True, we know from the clinical standpoint the influence of too much proteids or starch itt the diet; but from theoretical considerations their explanation is difficult.
A few words must be devoted to the subject of the amount of energy needed for its development by the infant. Rubner and Heubner made the first complete investigations of infant metabolism (including those substances which are exereted in gaseous form) which were directed to the quantitative determination of the energies remaining in the body as the result of the utilization of the food stuff; in other words they tried to establish a balance of energy. The details of the experi ments cannot be discussed here. Heubner concluded from his observa tions of the food requirements of infants that the work of digestion was much more considerable when the ehild was artifically fed than when nursed at the breast.
On this basis he suggests an explanation for the occurrence of infantile atrophy% The work of digestion may be abnormally increased (according to Heubner) by congenital weakness of the intestinal tract or that produeed by disease, so that of the calories introduced so large an amount is required for the work of digestion,--henee is lost for the body since the heat is dissipated,—that not enough remains for the work of assimilation; in fact some of the body substance neecls to be disassimilated to furnish the energy required. In view of the clinical facts these theories are very plausible and interesting, they still lack absolute scientific proof of their correctness.
We must now consider the practical importance in the estimation of the food-requirements of the sick infant of Heubner's quotient of energy. First we must remember that we should not judge a food (for infants or adults) solely by its dynamic value, but that the form in which we give the required energy, to the sick infant is all important. A child injured by overfeeding with fat will not regover on a mixture containing much fat, even if it represents a sufficient number of calories; the first indi cation here is to change to a diet with low fat and more carbohydrate, afterwards the quantity of energy required may be regulated.
Lately Czerny and Keller have suggested the classification of the disturbances of nutrition in infancy on a new basis, and have thereby rendered practical service to the clinician. These authors sought to establish clinical pictures of disease based on pathological-chemical processes (nillk-foocl injury, starchy-food injury, albuminous-food injury, etc.); and even if the latter must be considered still only as probabilities, they constitute a framework for our future investigations into the pathological-chemical causes of disorders of nutrition in infancy.