One of the most striking features of the present century is the progress of science and its effects on almost every aspect of social life. Building on the foundation laid by the predecessors, the scientists of today are carrying their investigation into ever-widening fields of knowledge. Modern civilization depends largely on the scientist and inventor. We depend on the doctor who seeks the cause and cure of disease, the chemist who analyses our food and purifies our water, the entomologist who wages war on the insect pests, the engineer who conquers time and space, and a host of other specialists who aid in the development of agriculture and industry. The advance of science and technology has brought the different parts of the world into closer touch with one another than ever before. We are able to reach distant lands within a very short time.