When heat treatments of the same sporicidal effectiveness were given, directly heated ultra-high-temperature sterilized milk gave twice as much sediment as indirectly heated milk after storage at room temperature for 100 days. Both types of process reduced the rate of clotting of the milk with pepsin and rennin, but the effect of the indirect process was markedly greater than that of the direct process.

The electrophoretic mobilities of proteases present in gastric juice taken within 10 h of birth from 5 healthy, premature infants were compared with calf chymosin, pig pepsin A and human adult gastric juice. The juice from 2 infants contained predominately a chymosin-like enzyme, another had almost exclusively pepsins similar to those of the adult juice, while the other two contained a mixture of both. The pepsins consisted of two elements, probably pepsin A (EC 3.4.23.1), and pepsin C (EC 3.4.23.3). Single radial immunodiffusion gave a definite reaction to calf anti-chymosin serum in five samples taken from a further 17 infants. These results indicate that some human infants secrete chymosin. The reaction in the immunodiffusion assay indicated a much lower enzyme activity than that implied from electrophoretic separations. It is suggested that species differences resulted in poor cross-reactivity of the antiserum.

I . The food intake, pancreas weight and trypsin (EC 3 . 4 . 2 1 . 4 ) and a-chymotrypsin (EC 3 . 4 . 2 1 . I ) activities in the pancreas were measured in rats during pregnancy and lactation and after the young were weaned.2. All the quantities measured increased significantly during lactation and had returned to their original values by 4 weeks after weaning. Food intake and pancreas weight were highest after the second week of lactation. Total trypsin and a-chymotrypsin activity, and the activity per g tissue, fell during pregnancy and rose during lactation, reaching a maximum I week after weaning. 3.From these and other results it is suggested that the hypertrophy and hypersecretion of pregnancy and lactation are initiated by changes in insulin secretion and mediated by the trophic effects of gut hormones, and that differences in the nature and timing of the response may be controlled by nutrient availability.

I . Changes in blood sugar levels after giving carbohydrates have been used to assess carbo-2. Glucose, galactose and lactose were readily utilized by all calves; the utilization of glucose 3. Maltose and fructose utilization was low in young calves and increased slightly with age. 4. Sucrose and starch were not utilized. 5. Studies with three older pre-ruminant calves (aged 53, 88 and 106 days) in which the carbohydrates were infused into the proximal duodenum showed that glucose, galactose, lactose and xylose all caused marked increases in the level of blood reducing sugar, whereas fructose and sucrose caused no increase, and maltose was intermediate. Xylose and galactose caused very little change in the blood glucose concentration.6. It appeared that preferential uptake occurred of glucose from a glucose-galactose mixture. 7.A non-linear relationship was found between the concentration of glucose or galactose hydrate utilization in pre-ruminant calves aged between 10 and 50 days.and galactose increased with age, whereas that of lactose remained constant.infused and the increase in the level of blood reducing sugar.

Summarygiven formulas containing predominantly whey proteins did Abbreviation DM, dry matterSimilarities in the digestive system of man and the pig suggest that results of studies on digestion and nutrition in the pig may be applicable to man (9). Some similarities in neonatal glucose metabolism have also been demonstrated (1 3). Other studies in neonatal pigs have assumed that results may be relevant, for example, in studies on protein nutrition (28, 23). However, no systematic comparisons of protein utilization have been made between the two species during the neonatal period. Such comparisons must inherently be rather superficial since ethical considerations limit the data on protein nutrition and digestion from infants to parameters of growth, nutrient retention, and analyses of blood.Between species, there is considerable variation in the proportions of casein and whey proteins in the protein of the milk. Whey proteins account for about 20, 50, and 80% of the total protein in bovine (26), porcine (27), and human milks (16), respectively. The desire to "humanize" dried milk formulas for infants which were previously based on unmodified bovine milk gave rise to studies in which formulas containing predominantly casein or whey protein were compared in infants. At the time of these studies, it was believed that whey proteins contributed only 60% of the total protein in human milk (16). Although not all differences were statistically significant, low birth weight infants show improved N retention (2) and reduced concentrations of urea in plasma (24), suggesting a better utilization of the protein.Increasing the protein concentrations in the milk also reduced the efficiency of protein utilization (24). In term infants, plasma urea concentration was also reduced by a formula containing predominantly whey proteins (19), but a recent study detected no differences in the utilization of casein and whey proteins (17). As it was desired to test the validity of the neonatal pig as a model for infant nutrition, milks containing either casein or whey as the predominant protein have been compared at two levels of protein intake in neonatal pigs. In view ofthe substantial proportion of whey proteins in sow's milk, enriching a milk substitute with whey proteins could also have important implications in the rearing of early weaned pigs.These studies have also been extended to compare gastric digestion and emptying following slaughter under standardized conditions. I n vifro studies in our laboratory (unpublished) showed that the coagulation time following the addition of bovine chymosin was inversely related to the casein content of the milks. Therefore, an increase in the proportion of whey protein might increase the rate of gastric emptying. Previous work has shown that whole cow's milk quickly coagulated in the stomach of the 4-week-old pig, followed by rapid draining of the whey (6). Also, the amount of dry matter in the stomach was usually decreased when milk was replaced by noncoagulating proteins derived from soybea...