Abstract
Estimates are given of the sodium-potassium balance in the erythrocytes of 16 Australian Merino and Merino cross lambs at ages ranging from to 98 days. The [Na+] values rose and the [K+] values fell from birth till an age of approximately 60 days, after which each variable fluctuated about a value comparable with those obtained for the dams of the same lambs, all of which were adult Merinos. Curves were fitted up to 57 days, their equations being y[Na+]=21�47 +2�63x-O�0203x' and y[K+] =99�60-2�78x+O�0221x' (x = age in days).