The whole question became suddenly actual when in 1959 KARELITZ et al. published their observations of 44 premature infants from the 10 th day of life to the day of achieving a weight of 2000 g, placing them in one of the three feeding groups : high protein --low fat milk, evaporated milk and a lactic acid --evaporated milk mixture. Infants in the last group were pale, showed an unhappy "facies" and the gain in weight, expressed in grams pro kilogram of body weight per day, was less than that of infants in the other two groups. We do not believe that KAttELITZ'S study allows a definite conclusion, as the periods of observation differed, so that the infants studied form a heterogenous group. Additionally, the concentration of the sour milk formula (17,5~o) is much higher than what is usually recommended for prematures. Two years later, the same research group reported metabolic studies on 36 premature infants, showing once more that the weight gain of infants receiving milk to which lactic acid was added was lower than that of a controle group. In this experimental group, they also found a significant decrease of venous CO 2 and pI-l. The reason for the acidosis was the increased excretion of lactate in the urine. However, we would like to draw the attention on the 0,85 g lactic acid added to i00 ml formula, as this way the lactic acid is twice as concentrated as in the acidified ~ cow's milk which is recommended for premature infants. This difference may well be the reason of the results observed.
SALAZA~ DE SOUSA and his group published in 1963 a paper concerning 20 premature infants who received a I~ cow's milk formula, and 20 other infants receiving an acidified I~ cow's milk formula. They found that the latter group showed a poorer weight gain, a lower capillary pH, a lower CO S content and a higher lactic acid level in plasma.
In this paper unfortunately one cannot find details concerning the exact amount of acid which was added to the formnla, and finally the groups were very heterogenous, especially as there was only a comparison of the values of the first and last day of the period of observation, which varied between 17 and 60 days. The authors did not mention the age of the infants at the time of the study.
RATH controlled the weight gain in a group of newborn infants, receiving an acidified formula and was satisfied with the results. He does not mention any control group and did not determine the acid-base balance.
So far no one has an answer to the question of the role of lactic acid in the production of acidosis. GOLD~A~ and his group observed an increase in serum lactic acid level from 1,4 to 2,2 mEq/1 in premature infants fed lactic acid milk. There was no increase in the control group.
To determine whether there was a disturbance in the metabolism of lactic acid, they injected lactate intravenously and found no difference