In all civilised countries the subject of infant feeding has, of late years, been attracting much attention, and in Germany, France, America, and our own country much has been done to unravel medical difficulties, to avert unnecessary sources of evil, and to grapple with many of those social and economic problems which are so intimately bound up with the supply and administration of nourishment for the young child.

In our own country, all the different conditions connected with the subject - the conditions of life, of food-supply, climate, environment in general - all, naturally, vary to a certain extent from those in other countries.

1 By Dr Dingwall Fordyce.

Thus, while at the base of the subject of the scientific practice of the feeding of infants and young children there rest broad laws applicable on all occasions, yet it is not surprising to find that the methods successfully employed in one country vary considerably from those employed in another, where the various factors entering into the life of the child are modified to a considerable degree. The broad basal laws, the scientific principles, are, however, such as demand consideration and recognition from all medical men to whose charge is entrusted the medical supervision of early childhood.

Physiological Characteristics Of Early Childhood - (1) The Digestive Powers

At the period of birth, and immediately after it, the secretion of saliva by the infant is small in amount. As the weeks pass, this amount rapidly increases, and by the time the infant is two or three months old the secretion is free. Yet its digestive power is still limited, and it's composition is different to that in adults. The starch-splitting ferment, ptyalin, is a constituent of the salivary secretion which is present in extremely minute quantities during the early weeks and months of life; as life advances it increases in amount - by the third or fourth month it may be present in quite considerable quantities, and at about the period of the commencement of the primary dentition (the sixth to the tenth month) it increases rapidly to large proportions. Starch, therefore, if occurring in the infant's food, will, up to at least the sixth month of life, pass into the stomach very largely unaltered by the salivary secretion; while, after this period, the average infant will be found to possess, in its saliva, the means of initiating the digestion of a not inconsiderable amount of starchy food.

During the early months of life the natural food of the infant is his mother's milk. This milk is obtained by the process of sucking from the maternal breast; mastication is unnecessary, the jaws are not called upon for active exercise, and the secretion of saliva is comparatively small in amount and poor in digestive capacity. With the development and eruption of teeth, marked changes occur. The masticatory powers now call for development, the jaws demand exercise for proper growth, and the digestive quality and the quantity of the saliva increase markedly. With the eruption of succeeding teeth the masticatory and digestive capabilities progressively increase, and by the end of the second year are in an advanced stage of development.

The position of the stomach in infancy is more upright than that which it ultimately assumes, and as a consequence the regurgitation of the gastric contents is a simple process. Of the ingredients of the gastric juice, rennin is present from birth in considerable amount; while pepsin and hydrochloric acid, though secreted shortly after birth, are present at first in only small amount. The digestive powers of the gastric juice are therefore at first very limited, and it appears that at this period the greater part of digestion is carried on in the intestine. The reaction between human milk and rennin results in but very fine curd-formation, and, consequently, a large quantity of the milk passes rapidly through the pylorus to undergo the major part of digestion in the small intestine. The gastric mucous membrane is sensitive and intolerant of the presence of foreign bodies, particularly during the early months of life, and large, tough curds - such as those of cow's milk - and, at a later period, lumps of food or irritating liquids are badly borne, and usually quickly rejected by vomiting.

The secretion of bile is, on the other hand, free from birth onwards. The liver is comparatively large at birth, its activity considerable, and its digestive powers well developed. Likewise, the digestive powers of the pancreatic secretion are considerable, with this marked limitation, however - the starch-digesting power is largely in abeyance. Amylopsin in the pancreatic juice, like ptyalin in the saliva, is, during the early months of life, chiefly conspicuous by its absence; the bodily powers of digesting starch develop gradually only after birth, and, until the period of the commencement of the first dentition, are extremely limited. In the small intestine the greater part of digestion takes place. The intestines in infancy are very freely movable, and as this is a period when muscular spasm and muscular inco-ordination are of common occurrence, it is readily seen how vomiting, diarrhoea, and intussusception easily occur. Examination of the faeces of a breast-fed infant shows that bacteria are present in abundance, and that they are mostly positive in reaction to Gram's stain. Bacillus bifidus is here the dominant form (Herter); it is anti-putrefactive, does not attack protein, and forms lactic acid on sugar media.

A variety of other organisms are also present, among them Bacillus coli (Gram negative) and Bacillus lactis aerogenes.

In the case of bottle-fed infants the number of bacterial forms present is greater than in breast-fed infants, and the dominant type is not the Bacillus bifidus but the Bacillus coli. The difference in the bacterial flora in the two cases is important, because of the tendency of Bacillus coli to further putrefactive changes.

In both breast- and bottle-fed babies very little putrefactive decomposition ordinarily occurs in the intestine, and it is well here to note that milk has a restraining effect upon intestinal putrefactive processes. With an increased and varied diet different bacterial conditions are obtained in the intestine, although putrefactive processes as compared with adult life are not active. During the first few weeks of life the infant has three or four movements of the bowels daily; later, two movements daily are common. It is important to note the character of these stools: they consist of some 2 or 3 ounces of a light yellow, homogeneous, semisolid fluid, with a faintly acid reaction to litmus paper.

As regards the digestive processes, from the point of view of the foodstuffs it has been shown that the power of the newborn baby to digest starch is very limited. Normally this power gradually increases in amount until the period of the first dentition, when its development takes place rapidly. Sugar is readily digested even in early infancy, and forms an important part of the infant's diet. The readiness with which it undergoes fermentative change - more particularly under the action of the lactic acid bacillus - results in its tendency, when present in excess in the food, to cause gastro-intestinal disturbance, and such disturbances associated with, or caused by, fermentative processes are, consequently, common in early childhood.

Fat and carbohydrate are the chief sources of animal heat: in the adult the value of fat in this respect is, in an ordinary diet, markedly less than that of carbohydrate; in the infant the conditions are reversed, fat being of greater value than carbohydrate. Fat is urgently needed by the body cells in childhood; it is as a rule readily digested at this period, and it assists in the absorption of mineral salts.

At no period of life are the differences between the varieties of protein more clearly demonstrated than in earliest infancy. The greater bulk of the curd resulting from the ingestion of cow's milk compared with that of human milk is largely due to the difference in the relative proportions of the protein constituents in the two milks, and is a cause of many of the difficulties associated with the artificial feeding of infants. The digestive functions of the stomach are constantly stimulated to fuller development as age advances, owing to the ever-changing amount and quality of the fluid secreted and the consequent changing reactions between it and the milk. By the period of the first dentition all the digestive juices are fully active, and are secreted freely; the stomach is capable of containing larger meals, and the intervals between meals can be considerably lengthened. The anatomical peculiarities of the infant stomach have become less marked, the susceptibility of the gastro-intestinal mucous membrane to local sources of irritation is much diminished, and the general muscular tone has developed considerably.

(2) The Bodily Needs

In practice, the correct recognition of the individual influences which affect the amount of food required, and of the nature of these influences, is necessary for the regulation of a suitable dietary.

Of such factors bodily growth is one of the most important. In childhood, assimilative powers are great and growth is active - so powerful, indeed, is this tendency towards nitrogen-retention that even in times of illness, when the child is receiving a meagre diet, poor in protein, and emaciation is occurring, yet nitrogen is retained by the cells, and growth takes place.

In the case of a child the calls of the organism for growth necessitate an ample diet, and, more particularly, an adequate supply of nitrogenous material. Owing to the great surface extent of the child in relation to his bulk, and the consequent considerable loss of heat, his need of a relatively large supply of non-nitrogenous food as compared with the adult is also marked. In this relation, as has previously been noted, fat is of geater value than carbohydrate to the infant, and thus we find that abundance of fat is one of the chief characteristics of the food in infancy and early childhood.