In 1851, Gall Bouden found a way to take some of the water from milk. 64. This made milk keep longer. A few years later, Louis Peter introduced a way to kill the bacteria (细菌) in milk. Next a special milk bottle (瓶子) was made. 65. Then machines that could fill bottles with milk were invented. These inventions show that milk has been important food for a long time. And it will probably go on to be so as long as there are animals that give milk.