214 



E. M. WiDDOwsoN AND R. A. McCance 



which has been done on kidney shoes in vitro (Robinson, 1954), 

 and on renal glutaminase and ammonia production (Hines 

 and McCance, 1954) goes to show that, weight for weight, the 

 kidney of the newborn of other species contains less glutamin- 

 ase and produces less ammonia than that of the adult. Fig. 3 

 shows that the total amount of ammonia excreted per kg. of 

 body weight was in fact small in the first two days, but that 

 by a week, when the baby was taking in three times as much 

 protein as the adult per kg. of body weight, it had risen above 

 the adult level. The ability to form ammonia in response to 

 an acid load in the first day or two of life has not yet been 



m-inole/kg./24h. 

 0-8. 



0-6 



O 4? 



Adult 



O- 24- 7- I 

 24h 48h. 8day year 



Fig. 3. The amount of ammonia 

 excreted. 



studied in man, but Cort and McCance (1954) found it to be 

 smaller in puppies two days old than in adult dogs. The 

 matter requires further investigation. 



Fig. 4 shows the excretion of ammonia in millimoles/24 

 hours divided by the glomerular filtration rate (as measured 

 by the endogenous creatinine clearance) in ml. /minute. It 

 was possible to calculate this ratio for the urine passed at 

 birth, even though the rate of urine flow before birth was not 

 known, because the two functions being compared are both 

 expressed in terms of rates of urine secretion. The excretion 

 of ammonia was high in utero and in the newborn period in 

 relation to glomerular filtration rate. The glomerular filtration 

 rate at this time of life is very low by adult standards, and if 

 the endogenous creatinine clearance is a true measure of it, 



