10 PHYSIOLOGY OF THE NEW-BORN INFANT. 



cent of the birth-weight. Trepper 1 has concluded that the percentage 

 loss was greatest with weak, undeveloped infants, least with those of 

 average weight, increasing again, not only absolutely but relatively, 

 with large infants because of the greater trauma during birth. 



But the loss in body-weight of the new-born infant may not be taken 

 as an index of its physiological needs for nourishment, as an analysis 

 of the character of this loss in weight shows us that there are two 

 distinct causes: (1) mechanical and (2) physiological. 



Within a few hours after birth the infant passes urine and meconium 

 and at times regurgitates allantoic fluid from the stomach. No one of 

 these can be said to represent a loss due to the physiological disintegra- 

 tion of body-substance, but they should all be classified under the head 

 of mechanical loss. 



Subsequently there is a loss of body-material or body-reserve which 

 should be considered as definitely disintegrative. When a previously 

 nourished organism is subjected to complete inanition or withdrawal 

 of food, there is in all cases a marked loss in weight during the first 

 period of the fast, and as the fast progresses the loss becomes consider- 

 ably less per unit of time. This is strikingly noted in experiments with 

 fasting animals, and, indeed, in those with man, and receives a logical 

 explanation in view of modern studies which show that there is an excess- 

 ive water-loss during the earlier stages of inanition. Exactly the same 

 conditions may be said to exist in the case of new-born infants. Before 

 birth the infant was in a moist environment and the body was therefore 

 surcharged with water. A not inconsiderable amount of this may be 

 lost very shortly after birth through vaporization from the skin and 

 lungs, particularly when active crying takes place. This water should 

 be considered as preformed water existing in the body. 



But the most important physiological loss is that due to the actual 

 oxidation of body-substance as a result of metabolism. With the first 

 moment after delivery and as soon as the lungs have become filled with 

 air, the infant begins to oxidize body-substance, this material being 

 chiefly fat, with some protein and some carbohydrate. This material 

 is carried off in the form of carbon dioxide and of oxidized organic 

 hydrogen, and thus contributes its quota to the physiological loss. 



Since the loss of meconium, allantoic fluid, and urine, and even of 

 preformed water, is not accompanied by energy transformations and 

 the liberation of heat, we may estimate the true physiological loss by 

 determining the energy loss either directly or, what is more practicable, 

 by the indirect method of measuring the carbon-dioxide output and the 

 oxygen consumption. 



Although it is a popular conception that the new-born infant has a 

 very much larger metabolism than has the adult, evidence that we 



'Trcpper, Ueber die Gewichtsabnahme der Neugeborenen, Inaug. Diss., Giessen, 1913. 



