Milk coming from ill-nourished, half-fed cows, having no surplus of food beyond minimum requirements of nature, is injurious, and may be a source of disease. Cows deprived of an abundance of good water, ventilation, and exercise, secrete impure and dangerous milk, which may be loaded with gases, animalcule and fever-germs. The milk from old, debilitated cows fed on grains or overstimulating food, is also imperfect and unhealthy to a variable degree. The nervous condition of the cow at the time of milking determines the purity of the milk. If this is neglected, the milk is an active source of disease, and is positively dangerous and fatal.