The first milk looks like ordinary milk (breast milk), or if the baby is being fed from the bottle, it looks just like the mixture in the bottle. It not only looks like what it took, but it smells just like it. Now examine the other; we find it looks like curdled milk, it is lumpy, and we immediately can tell that it is sour, because it smells sour and looks sour. The explanation of the first overflow (immediately after the feeding) was the too great quantity; the explanation of the second overflow (one-half hour or so after the feeding), is the wrong quality of milk. The quantity was right because none overflowed right after the feeding, but the quality was wrong. Again, it is not the baby's stomach that is at fault,--it is the quality of the milk. How do we know this? Because of what takes place in the baby's stomach during the one-half hour between the feeding and the time of the overflow of the sour milk. The quantity being right, why should the baby have any trouble if the quality is correct? It should not. Therefore by changing the quality (not the quantity as in the former case) we cure the trouble, thus proving the quality of the milk to be at fault. What took place in the baby's stomach in the intervening half hour? The quality being wrong, the little stomach could not digest the mixture quick enough. Fermentation set in, gas was evolved, and as the stomach was full before the gas was manufactured (and as more and more gas is manufactured when food ferments), the stomach overflowed and out of the baby's mouth comes gas, and sour, fermenting, curdled milk. This process goes on until fermentation stops, or until the little stomach has just enough left to fill it and no more. But think what this is,--a sour mass of rotting, indigestible, curdled milk,--and that is what this baby is expected to live and thrive on. Some babies seem to have trouble from the very first day of life. Either they will not retain the food, or the food fails to agree with them. If the baby is put upon artificial food at once, these troubles are, of course, not unexpected (because the right artificial food may not be first chosen for the particular baby), but it is not always the artificially fed baby that gives us trouble, and it is sometimes difficult to find the cause for such trouble in a baby who has had nothing but its mother's milk since it was born. The cause of stomach trouble in a baby a few days old, fed exclusively on mother's milk, is invariably to be found in the quality of the milk. The quality of the mother's milk may be affected in a number of ways which will render it unfit for the baby. For example, if the mother for any reason becomes sick, and has a high fever shortly after confinement, it will affect her milk and render it unfit temporarily.