Development of Acid-Base Control 211 



on four additional babies on the 7th to 8th day. Of the seven 

 babies investigated one week after birth, six were breastfed 

 and the seventh was fed on Ostermilk. Samples of blood 

 have been taken from the cord at birth, and from the femoral 

 vein at 48 hours and seven days. Urine has also been collected 

 for 24 hours from one child aged eight months and from one 

 aged one year, while six normal men and women have pro- 

 vided 24-hour urine collections to serve as the adult com- 

 parisons. The urines were collected and stored under toluene. 

 Determinations of pH, titratable acid, ammonia, creatinine, 

 phosphate, citrate and sulphate have been made on the urine, 

 and the sera have been analysed for creatinine, CO 2, chloride, 

 sodium and potassium. 



The excretion of surplus anions 



Fig. 1 shows the millimoles of surplus anions not combined 

 with fixed base (i.e. titratable acid plus ammonium salts) 

 excreted by the infants on the first, second and seventh days 

 of life and by the older infants. A figure for the adults is 

 indicated also. All the values are expressed per kg. of body 

 weight per day. The average pH of the adult urine was 6 or 

 a little over, while that of the babies was between 5 • 5 and 5 • 8, 

 and this has to be taken into account in considering some of 

 the results. The urine passed in the first and second 24 hours of 

 life contained less surplus anions per kg. of body weight than 

 that of the adults although the pH of the urine was lower, 

 which would have led one to expect a higher rather than a 

 lower anion excretion. This low rate of excretion was quite 

 sufficient to maintain the acid-base balance of the body, for 

 the serum CO 2 and chloride did not change. It is to be 

 attributed to the fact that the urine contains very little 

 phosphate or sulphate at this period (McCance and von Finck, 

 1947, and see later), owing to the small breakdown of tissue 

 protein (McCance and Strangeways, 1954). By the seventh 

 day the babies were taking nearly 500 ml. of breast milk a 

 day, which contained 9-5 g. protein or about 3 g./kg., and 

 they were passing about three times as much urine per kg. of 



