(ASSIMILATION, DISINTEGRATION) In the metabolism of infancy there is 011C fact of great importance that characterizes it, namely, that the processes of growth normally bring about assimilation and retention of the inaterials in the food necessary for the development of the body. We must, therefore, in vestigate to what degree pathological conditions can influence the normal retention of infant food constituents. Many such investigations have been directed to determine the fate of the nitrogen in the child's food, and give the apparently- paradoxical result that under almost all condi tions, even in sick infants whose body weight. is at a standstill or who are losing weight, a retention of nitrogen nevertheless results. This is in agreement with Ctimerer's observations that even atrophic infants show a. growth in length and indicates the extraordinary intensity of the stimulus to growth within the body. The misproportion between this retention of albumin and a standstill or loss of body weight indi cates plainly that other food-stuffs must pass unutilized through the body, and NV C are now in a position to state definitely which food constit uent is primarily at fault. The trite statement that a child which is losing in weight or which is only holding its own becotnes thin (that is, becomes poor in fat), has been confirmed by Steinitz's analyses of the total ash from the bodies of infants. The only marked difference in the chemical composition between the body of the healthy child and that of the infant who had' died from severe illness, is the notable difference in the fat content,.
What we know from metabolism experiments on the retention of water in the body agrees well with our clinical experience. -Whereas the physiological assimilation of water amounts to GO per cent. of the total assimilation, according to Carnerer, and whereas this proportion is the same in infants who are gaining regularly in weight, under pathological conditions we find frequently very great changes in the body weight, either up or down, which can only be brought about by corresponding alterations in the watery content of the body,—for this reason, that the assinailation and excretion of the other constituents could not take place to the same extent in the same time. Our a priori assumption is herewith confirmed by exact investigation (Freund).
-Whereas the phosphorus in milk (Keller) is usually retained well even by sick children (especially that of wornen's milk), and its assimi lation runs more or less closely parallel to that of nitrogen, the chlorides on the other hand are apt to vary with the alterations in the water content of the body (Freund). Alkalies can be excreted by the intestine
in such large amounts as the result of a diet containing plentiful amounts of fat, that the body may lose a considerable part of its alkali.
In febrile conditions, as we have already mentioned, the body may lose lime in excess. 'We have little knowledge of the causation of other anomalies in the retention of lime salts, the end results of which are seen in the defective ossification of the rachitic skeleton as well as in the diminished content in lime of the brain in the condition known as tetany (according to Quest's investigations, which require confirmation).
The processes of disassinrilation in the body, the so-called inter mediary- metabolism, also interest us from the pathological standpoint. Of these we as.sume rather than know that they deviate from the normal in the sick child. The sum of the processes of oxidation which bring about clisassimilation, has been studied in chronic diseases of infancy from two standpoints. First of all the pos.sibility exists that excessive heightening of oxidative processes interferes with the normal processes of assimilation and so creates conditions akin to those in infantile atro phy. The hypothesis which Bendix put forth with regard to these cases, has not been confirmed by the investigations hitherto made of the excretion of carbonic acid by atrophic infants. On the contrary Rubner and lleubner found no decided deviation front the normal, and Poppi even found a diminished excretion of carbonic acid. In the second place we have good reason to believe that there is a diminution of the normal processes of oxidation in set-ere cachexias in infancy, and certain facts seems to substantiate this view. Pfaundler has shown that there is functional loss of the oxidizing ferment of the liver in cer tain cases; moreover we know that the power of oxidizing benzol into phenol is very much diminished in the very sick infant (Freund). Re cent experimentation in the same line by Ludwig F. Meyer has demon strated diminished capacity of the infant organism to oxidize further the phenol taken into the body. In this place we must mention that French authors have ascribed an important role to the process of dimin ished oxidation thradytrophy). These cases are characterized by an excess of uric acid in the circulation and a great variety- of pathological phenomena, the so-called "Arthritisin". On the basis of a critical study by Gfippert we must consider that the pathological-chemical basis of this constitutional disease remains still in the realms of speculation.