INTRODUCTION. 9 



First, the infant must keep up its vitality. In the prenatal condition 

 it has been in a moist, warm medium, with no loss of heat by radiation 

 or by the vaporization of water. By birth it is suddenly thrust into 

 a much less moist and often cold environment. It is currently believed 

 that this change is in some way actually beneficial, since it acts as a 

 stimulus to the vital activities of the infant. But immediately after 

 birth the child is required to make up for the heat lost by radiation, 

 which is considerable, and for that used in the vaporization of water 

 from the body-surface. In the few days subsequent to the birth the 

 infant's heat-regulating mechanism is extremely imperfect. It is first 

 called into play as soon as the child is delivered. A bath is usually 

 given shortly after the delivery, which, with its attendant exposure 

 of the body, unquestionably increases the heat loss. There is, however, 

 almost invariably an increased heat-production as the result of muscular 

 activity and frequently loud, vigorous crying. 



We may classify the new-born infant's needs under two gross cate- 

 gories: first, the need for maintenance, and second, the need for 

 growth. Since, in our discussion, we are interested for the most part 

 in the consideration of the metabolism during the first week of life, we 

 may properly at this time omit consideration of the question of growth 

 and confine ourselves exclusively to the maintenance requirements. The 

 question, then, is : Can the infant in the first week of life obtain sufficient 

 nourishment from its mother, even a normal mother, to maintain its 

 vital activities without loss of body-substance? An examination of the 

 records of body-weight will be of interest in this connection, for a loss 

 in weight, if any, may be considered a crude index of the infant's needs. 



LOSS IN BODY-WEIGHT. 



Shortly after birth there is normally a very considerable loss in body- 

 weight. The average duration of this loss in weight is 2 to 3 days, the 

 length of time depending upon when the mother's milk-supply is suf- 

 ficiently established to provide the infant with enough nourishment for 

 its needs. If an infant continues to lose weight after the fourth day 

 the cause must be pathological. As may naturally be expected, the 

 time and amount of the secretion of the breast-milk are the principal 

 factors in determining the amount of weight lost. The loss of weight 

 varies according to different investigators, but usually lies between 

 150 and 300 grams, 1 with an extreme high figure of 700 grams. 2 A loss 

 of even 400 to 500 grams has been observed with infants which have 

 shown no pathological disturbance at the time or later. In general, 

 the smaller the baby is at birth, the greater will be the relative propor- 

 tion of the weight lost, the usual proportion being between 6 and 9 per 



1 von Reuss, Die Krankheiten des Neugeborenen, Berlin, 1914, p. 2. 



2 Czerny and Keller, Des Kindea Ernahrung, Ernahrungsstorungen und Ernahrungstherapie, 

 Leipsic and Vienna, 1906, 1, p. 554. 



