Robert Koch.--Another name associated with the battle against disease germs is that of Robert Koch. Born in Klausthal, Hanover, in 1843, he later became a practicing physician, and about 1880 was called to Berlin to become a member of the sanitary commission and professor in the school of medicine. In 1881 he discovered the germ that causes tuberculosis and two years later the germ that causes Asiatic cholera. His later work has been directed toward the discovery of a cure for tuberculosis and other germ diseases. As yet, however, no certain cure seems to have been found. Lister and Antiseptic Treatment of Wounds.--A third great benefactor of mankind was Sir Joseph Lister, an Englishman who was born in 1827. As a professor of surgery he first applied antiseptics in the operating room. By means of the use of carbolic acid or other antiseptics on the surface of wounds, on instruments, and on the hands and clothing of the operating surgeons, disease germs were prevented from taking a foothold in the wounds. Thus blood poisoning was prevented. This single discovery has done more to prevent death after operations than any other of recent time. Modern Workers on the Blood.--At the present time several names stand out among investigators on the blood. Paul Ehrlich, a German born in 1854, is justly famous for his work on the blood and its relation to immunity from certain diseases. His last great research has given to the world a specific against the dread disease syphilis. Another name associated with the blood is that of Elias Metchnikoff, a Russian. He was born in 1845. Metchnikoff first advanced the belief that the colorless blood corpuscles, or _phagocytes_, did service as the sanitary police of the body. He has found that there are several different kinds of colorless corpuscles, each having somewhat different work to do. Much of the modern work done by physiologists on the blood are directly founded on the discoveries of Metchnikoff. [Illustration: Charles Darwin, the grand old man of biology.] Heredity and Evolution. Charles Darwin.--There is still another important line of investigation in biology that we have not mentioned. This is the doctrine of evolution and the allied discoveries along the line of heredity. The development or evolution of plants and animals from simpler forms to the many and present complex forms of life have a practical bearing on the betterment of plants and animals, including man himself. The one name indelibly associated with the word evolution is that of Charles Darwin.