From this calculation it may he seen that the preservation of the proteid and ash content of the infant's and adult's body requires the introduction of 0.9 Gin. proteid for 100 Gin. proteid present in the body, and of 0.5 Gin. ash for 100 Gm. ash present. Older children perhaps require an introduction of 2 per cent. proteid to fulfil this purpose, the reasons for which need not be considered here.
The statistical method furnishes reliable values with regard to the introduction of the individual ash constituents. From Sokiller's anal yses the following values were calculated for a breast-fed infant on the eighth and the seventieth day of life, assuming the respective quanti ties of food in 24 hours to be 500 Gin. and SOO Gm. milk (values for 24 hours in milligrams).
Surprise may be felt that the introduction of and Cl on the seventieth day is much smaller than on the eighth day, while there is hardly any difference in the values for and SO,. The reason is that 100 Gm. milk on the eighth day of lactation contains at least 0.3 Gm. ash, while milk on the seventieth day contains hardly 0.2 Gm. ash. The amount of Nap and Cl diminishes very much, and the amount of K0, aml SO, decreases raffler considerably, but this loss is e(fual izc.‘(l by the increased amount of milk. The milk of both periods con tains the same amount of Cat), MO), or of those ash constituents which are concerned in the formation of bone. the increased amount of milk is of benefit. The reason why the fixed alkalies and CI are diminished is not known.
fabler shows that about .10 per cent. of the ash introduced into the body is retained. Iu regard to the individual constituents, it can he stated with certainty that less than 50 per cent. of the introduced fixed alkalies and Cl are retained, and more than 50 per cent. of the introduced CaO, MgO. and At present, it would he unsafe to give more detailed data, since the amounts entering into consideration are rather small and the difficulties of the analyses are therefore great. lt may be mentioned that in speaking about organic substances, "mineral" and constituents are by no means identical.
The metabolism of the artificially jol infant does not differ in prin ciple from that of the breast-fed, and it approaches the latter the nearer to the natural and the more rational the artificial feeding. The bottle fed infant secretes more urine on account of the increased introduction of liquid, and the amount of feces is larger. since more is given and
the food is not utilized so well. The requirement of calories is increased, as the baby under certain conditions is more restless and has to perform more work during digestion. In individual cases, the metabolism of the artificially fed infant differs so much with the different methods employed, that an exhaustive presentation of the subject here would lead us too far. For instance, feeding large quantities of slightly diluted cow's milk with a small addition of lactose causes a strong excess of casein and ash, particularly of Ca0 and and the N and ash con tent of urine and feces are consequently increased. When more diluted cow's milk, with perhaps an addition of fat (cream) and lactose. is fed, the urine and feces contain quantitatively but not qualitatively more nearly the same amount of ash and nitrogenous substances as in the case of a breast-fed infant, and so on.
The healthy artificially fed infant receives a larger amount of food than does the breast-fed infant. at least unless the desire of the infant for a larger amount of food is denied with great consistency. If the in fant remains perfectly healthy in spite of an excessive amount of food, to disregard entirely its cannot be advised. When the food requirement is much exceeded without injury to the infant, there will be a gain in weight. lint the increased peristalsis, the more abundant excretion of urine and feces, etc., render the infant always decidedly more restless, and it cries more than the breast-fed infant of the age. During the first weeks of life, the breast-fed infant generally sleeps when not occupied with nursing; later on it lies quietly cooing, etc. Formerly, when infants were much overfed, physicians could not under. stand how to account for the disposal of the food introduced. For neither the gain nor the solid substances of urine and feces could come anywhere near the amount introduced. The substances are oxidized and leave the body by means of the gaseous metabolism, and their combustion furnishes the energy required by the increased peristalsis, the restlessness, and the crying. This agrees with the demands of the theory and has been directly demonstrated in the fourth individual experiment of Heubner and Rubner.