4th. The pancreatic juice appears to have the function of digesting whatever alimentary substance has escaped digestion by the saliva, gastric juice, and bile. It is a clear, viscid liquid of alkaline reaction. It rapidly changes starch into glucose. It converts proteids into peptones and emulsifies fats. While the gastric juice requires an acid medium for the performance of its digestive function, the pancreatic juice requires one that is alkaline. This important fact should be borne in mind, that such a mistake as presenting pepsin with chalk mixture, or the extractum pancreatis with dilute muriatic acid, may be avoided.
5th. The intestinal secretions are mainly from the crypts of Lieberkühn, and their action in the digestive process is probably comparatively unimportant, but in some animals they have been found to digest starch. It will be observed that of all these secretions that which digests the largest number of nutritive principles is the pancreatic. It digests all those which are essential to the maintenance of life except fat, and it aids the bile in emulsifying fat.
One of the most important conferences in pædiatrics ever held convened at Salzburg in 1881 for the purpose of considering the diet of infants. Among those who participated in the discussion were men known throughout the world as authorities in children's diseases, such as Demme, Biedert, Gerhardt, Henoch, Steffen, Thomas, and Soltmann. None of the physicians present dissented from the following proposition of the chairman: That "all the advances made in physiology in respect to the digestive organs of children only go to prove that the mother's milk is the only true material which is quantitatively and qualitatively suited to the development of the child, which preserves the physiological functions of the organs of digestion, and under favorable circumstances of growth unfolds the whole organism in its completeness." All agreed that when the breast-milk fails animal milk is the best substitute. Henoch, who was one of the conference, expresses the same opinion in his well-known treatise on diseases of children, as follows: "Cow's milk is the best substitute for mother's milk during the entire period of infancy. I consider the administration of other substances advisable only when good cow's milk cannot be obtained or when it gives rise to constant vomiting and diarrhoea."
The many infants' foods contained in the shops were considered by the conference, and, in the words of the chairman, "Now and evermore it is unanimously agreed that these preparations can in no way be substituted for mother's milk, and as exclusive food during the first year are to be entirely and completely rejected." But, unfortunately, we soon learn by experience that animal milk, although it is the best of the substitutes for human milk, is, especially as dispensed in the cities, faulty. It is digested with difficulty by young infants, and is apt to cause in them diarrhoea and intestinal catarrh. Therefore in the hot months its use is very apt to act as one of the dietetic causes of the summer diarrhoea in infants exclusively fed upon it, unless it be specially prepared so as to more closely resemble human milk. The frequent unsatisfactory results of its use have led to the preparation of the many proprietary substitutes for human milk which the shops contain, and which have been so summarily discarded by the German conference.
Woman's milk in health is always alkaline. It has a specific gravity of 1.0317; cow's milk has a specific gravity of 1.029. That of cows stabled and fed upon other fodder than hay or grass is usually decidedly acid. That from cows in the country with good pasturage is said to be alkaline, but in two dairies in Central New York a hundred miles apart, in midsummer, with an abundant pasturage, two competent persons whom I requested to make the examinations found the milk slightly acid immediately after the milking in all the cows.
The following results of a large number of analyses of woman's and cow's milk, made by König and quoted by Leeds, and of several of the best known and most used preparations designed by their inventors to be substitutes for human milk, show how far these substitutes resemble the natural aliment in their chemical characters:
| Woman's Milk. | Cow's Milk. | |||||
| Mean. | Minimum. | Maximum. | Mean. | Minimum. | Maximum. | |
| Water | 87.09 | 83.69 | 90.90 | 87.41 | 80.32 | 91.50 |
| Total solids | 12.91 | 9.10 | 16.31 | 12.59 | 8.50 | 19.68 |
| Fat | 3.90 | 1.71 | 7.60 | 3.66 | 1.15 | 7.09 |
| Milk-sugar | 6.04 | 4.11 | 7.80 | 4.92 | 3.20 | 5.67 |
| Casein | 0.63 | 0.18 | 1.90 | 3.01 | 1.17 | 7.40 |
| Albumen | 1.31 | 0.39 | 2.35 | 0.75 | 0.21 | 5.04 |
| Albuminoids | 1.94 | 0.57 | 4.25 | 3.76 | 1.38 | 12.44 |
| Ash | 0.49 | 0.14 | ... | 0.70 | 0.50 | 0.87 |
The following analyses of the foods for infants found in the shops, and which are in common use, were made by Leeds of Stevens's Institute:
Farinaceous Foods.
| 1. Blair's Wheat Food. | 2. Hubbell's Wheat Food. | 3. Imperial Granum. | 4. Ridge's Food. | 5. "A.B.C." Cereal Milk. | 6. Robinson's Patent Barley. | |
| Water | 9.85 | 7.78 | 5.49 | 9.23 | 9.33 | 10.10 |
| Fat | 1.56 | 0.41 | 1.01 | 0.63 | 1.01 | 0.97 |
| Grape-sugar | 1.75 | 7.56 | Trace. | 2.40 | 4.60 | 3.08 |
| Cane-sugar | 1.71 | 4.87 | Trace. | 2.20 | 15.40 | 0.90 |
| Starch | 64.80 | 67.60 | 78.93 | 77.96 | 58.42 | 77.76 |
| Soluble carbohydrates | 13.69 | 14.29 | 3.56 | 5.19 | 20.00 | 4.11 |
| Albuminoids | 7.16 | 10.13 | 10.51 | 9.24 | 11.08 | 5.13 |
| Gum, cellulose, etc. | 2.94 | Undeterm'd. | 0.50 | ... | 1.16 | 1.93 |
| Ash | 1.06 | 1.00 | 1.16 | 0.60 | ... | 1.93 |