Such variations in the quality of the milk under different rations, occasionally affect the weak stomach of the new born, and as the same constitution is likely to predominate in the same herd, a number may be attacked together as a result of some change in feeding. Other conditions, however, lead to variation in quality. Hassall found that the morning milk of the cow furnished 7.5 per cent. of cream, while the evening milk gave 9.5 per cent. Boedecker found that morning milk had 10 per cent. of solids and evening milk 13 per cent. The first drawn at any milking is poorer in cream than that which is drawn last. The first may have only one-half or in extreme cases one-fourth of the cream that the strippings have. When the cow is in heat the milk not only contains more of the solids, but has granular and white blood cells like colostrum and often disagrees with the young animal. The milk of the young cow with her first calf is usually more watery than that of the adult, and that of the old one has a greater tendency to become acid. The longer the period which has elapsed since calving the greater the tendency to an excess of salts. Certain breeds like the Channel Island cattle produce an excess of butter fat (4–5 per cent.), whereas others like Holsteins, Ayrshires and Short Horns have less on an average (3–4 percent.), the casein and, it may be, the water predominating. Hence Jersey and Guernsey milk will scour calves which do well on that of one of these other breeds. Overkept, fermented and soured food tends to produce acidity and other changes in the milk. Old brewers’ grains, swill, and spoiled gluten meal, or ensilage, especially such as has been put up too green, are especially injurious to the milk. The milk of cows fed on raw Swedish turnips or cabbage acquires a bitter taste and odor. The milk of different genera of animals offer such strong contrasts that it is always dangerous to attempt to bring up the young of one genus upon the milk of another. The following table giving the composition of the milk in woman and each of the domestic mammals serves to illustrate this and to furnish a basis for adjustment: