The characteristic features of the infant's stomach are (1) its form and position, (2) its small capacity, and (3) its insignificant secretions.
According to Fleischmann, the cardia is fixed to the ]eft of the tenth dorsal vertebra, the pylorus is situated 2 to :1.5 cm. lower down in a prolongation of the middle sternal line, but rarely to the right of this line, and occasionally even somewhat to the left. When the stomach is empty, the pylorus forms its lowest point. In most cases the fundus is distinctly formed in the newborn, Intl it remains relatively flat for some time; and this, in conjunction with the position of the ex plains the frequency of vomiting and regurgitation in infants.
Pfaundler made a thorough study of the capacity of the stomach. From the first to the twelfth month he found the following values? 100, 110, _125, 140, .160, 1,.-;11, 200, 225, 251). 275, 20(1 c.c., (:3, •1:i, 6. GI, 83„ 0. 03 ounces) These figures can serve only as approximate guides for the size of a single meal, because considerable individual variations of the stomach capacity exist, and a part of the stomach contents passes into the in testine during drinking. The emptying of the stomach is dependent on the amount and the quality of the food. The stomach of the breast-fed infant is found empty after an hour and a half if small meals are given. If large meals are given, it takes two hours before the stomach is empty. The bottle-fed baby requires two and one-half to three hours to dispose of a large meal.
The secretory function of the stomach is already developed in the newborn. The mucous membrane of the embryo's stomach has an alka line reaction but in the stillborn the reaction is neutral or acid. It is always acid after ingestion of milk, and this is (Inc to the secretion of hydrochloric acid. At first the acid combines with the proteids and salts of the milk, and appears as free hydrochloric acid only after their saturation. In healthy breast-fed infants it is found about two hours after the meal in a concentration of about 0.1 per cent. In bottle-fed babies, free hydrochloric acid occurs much later or not at all, because the po of cow's milk to combine with the acid is much greater. There fore, the stomach contents of the bottle-fed infant are less antiseptic than are those of the breast-fed. Beside hydrochloric acid, the presence of lactic acid can be demonstrated in the infant's stomach contents. But nothing is known concerning its origin or its action.
The stomach of the infant contains rennin and pepsin the latter occurring in the embryo. The rennin causes the coagulation of the milk
casein in the stomach, the coagulum being dissolved by the hydrochloric acid. The casein of cow's milk coagulates much more completely than does that of human milk, and only a part of it is dissolved by the acid (Biedert). Mare's milk is the only milk resembling human milk in this regard, and this is poor in proteids (Langgaard).
Nothing definite is known about the action of pepsin in the infant's stomach. The stomach contents of the infant can be shown to contain peptone, but this could be due to the action of rennin or to bacterial decomposition.
The first scientific• investigations of the intestinal tract of the infant were conducted by Schwan. Be discovered the interesting fact that the length of the intestines as compared with the length of the body is con siderably greater in the infant than in the adult. This corresponds to the relatively greater requirement of food. The proportion of the length of the intestines to that of the body is in the infant about 6 or S to 1, in the adult 5 to 1. The absolute length of the intestines in the newborn is subject to wide individual variations, reaching about from 200 to 400 cm. to 12 feet). Oundobin found the length and height of the folds of the small intestine in the newborn less, and the number of the villi greater, than in the adult. The muscles of the intestines are relatively poorly developed in the newborn. The development of the glandular tissue is the same as in the adult, while the lymphatic apparatus (soli tary follicles and Peyer's patches) is relatively more developed. Orban and Weinland have lately studied the intestinal secretions. According to these authors, the secretion of the small intestine in the newborn contains a ferment. lactase, which is capable of decomposing lactose. Moro and Jakubowitsch, in contradiction to Korowin and Zweifel, affirmed that the pancreas secretion of the newborn possesses a diastolic activity, which is small when compared with the lipolvtic and proteolytic activity.
The liver, the second large abdominal gland, is of an extraordinary size in both faqus and infant. According to Barley the weight of the liver in relation to the body weight is in the newborn as 1 to 1S; in infancy as 1 to 20; at puberty as 1 to 30; in the adult as). to 35; in middle age as 1 to 40; in old age as 1 to 50.
The investigations of Zweifel show that the secretion of bile begins in the third month of foetal life. In the fifth month the formation of glycogen in the liver can he demonstrated.