At the present time we have at our disposal a mass of information with regard to the physiology of nutrition, which is of great value for the management of the infant's metabolism in health and disease. There are several reasons why this information has not been taken suffi cient notice of by physicians and hygienists. and why its significance is not duly recognized. One reason is that it is relatively so recent in date.
Another and more potent reason is that a great number of students of medicine and many physicians have not sufficient opportunity to apply themselves to pediatrics, and particularly to the physiology of child hood, during the period of their professional education. The new med ical examinations law in Germany requires proof from the candidate that he attended a children's hospital or dispensary regularly for half a year. According to the report of lleubner, in one-half of all the Prus sian universities neither exists, while the percentage of universities in which a thorough study of the physiology and pathology of the infant is made is still lower. One of the circumstances which may explain this surprising neglect of such an important branch of medicine can be found in the fact that even to-day many physicians, and even prominent clini cians, deny to pediatrics the right to exist as a specialty. Certainly, there is no sharp line of demarcation in the gradual transition from the child to the adult, which would permit a clean separation of the two subjects, and later childhood may be claimed with a certain degree of justification to belong to the sphere of internal medicine. But this cannot be said of the period of infancy and of early childhood.
A glance at the exterior build of a child shows that it can by no means be regarded as a small edition of an adult, and a closer examination of its anatomical and physiological conditions demonstrates a number of peculiarities which cannot be explained by a simple comparison with the adult, but require a special study. The period of childhood is not an indivisible unit, and with Vierordt we distinguish the following subdivisions: 21. Childhood: 1. Infancy: (a) Period of the newborn (first week of life).
(I) Period of suckling (until the eighth month of life).
(c) Period of the first dentition (until the fifth year of life).
2. Childhood, infancy to puberty.
B. Each of these periods has its physiological peculiarities, which in the period of the newborn and of the suckling are chiefly those of metab olism.
It is necessary at first to obtain information about the chemical composition of the infant's body, in order to understand the conditions of the metabolism at these periods of life.
On account of the great difficulties in procuring suitable material for•such investigations, the cadavers must be of normal individuals, and must not have suffered essential changes of the composition in con sequence of the causes of death,—t bus far we have only complete anal ysis of the newborn. It would be of the greatest advantage to know the composition of older children, so as to become acquainted with the changes brought about in the composition of the child by growth. Furthermore the no tare of growth in its different periods could be learned, which otherwise can only be accomplished with difficulty and uncer tainty. For instance, if the quantity and chemical ttuality of the intake and of the excretion of a child, the gaseous metabolism. are determined aml compared, the difference will show how much of the different substances (proteid, fat, water, ash) have remained in the body. All determinations of these differences suffer from the fact that all the errors of the experimentation accumulate themselves on the values for the differences, and if the differences are small, the result becomes very uncertain (see p . 372). At the time of the most energetic absolute and relative growth, which is toward the end of the first month of life. the daily gain in weight amounts to only about 30 { I ounce). This would mean about 4 per cent. of the total intake or excretion, and later on only two per cent. are accounted for in the gain of weight. The analyses of the newborn, however, permit us to draw conclusions in regard to the substances which combine to make up the gain, since we may be justified in that the composition of the bodies of chil dren varying in age a few weeks or months does not differ materially from that of the newborn. This assumption is strengthened by some analyses of pathological older children (Sominerfeld, Weigert. Steinitz).