In 1842-43 Gruby showed that Herpes tonsurans, a form of ringworm, is due to the fungus _Trichophyton tonsurans_. Klencke, in 1843, produced generalized tuberculosis in a rabbit by injecting tuberculous material into a vein in the ear, but did not carry his researches further. In 1843, Doctor Oliver Wendell Holmes wrote a paper in which he contended that puerperal fever was contagious. Liebert identified the _Peronospora infestans_ as the cause of one type of potato rot in 1845. The skin disease Pityriasis (tinea) versicolor was shown to be due to the _Microsporon furfur_ by Eichstedt in 1846. In 1847 Semmelweiss of Vienna recommended disinfection of the hands with chloride of lime by obstetricians because he believed with Holmes in the transmissibility of puerperal fever through poisons carried in this way from the dissecting room but his theories were ridiculed. [Illustration: PLATE III ROBERT KOCH] Pollender, in 1849, and Davaine and Rayer, in 1850, independently observed small rod-like bodies in the blood of sheep and cattle which had died of splenic fever (anthrax). That Egyptian chlorosis, afterward identified with Old World “hookworm disease,” is caused by the _Ankylostoma duodenale_ was shown by Greisinger in 1851. In the same year the _Schistosomum hematobium_ was shown to be the cause of the “Bilharzia disease” by Bilharz. Küchenmeister discovered the tapeworm, _Tænia solium_, in 1852, Cohn, an infectious disease of flies due to a parasitic fungus (_Empusa muscæ_) in 1855, and Zenker showed the connection between trichinosis of pork (“measly pork”) and human trichinosis (1860) as indicated above. The organisms just mentioned are, of course, not bacteria, but these discoveries proved conclusively that _living things of one kind or another, some large, most of them microscopic, could cause disease in other organisms_ and stimulated the search for other “living contagiums.” In 1863 Davaine, already mentioned, showed that anthrax could be transmitted from animal to animal by inoculation of blood, but only if the blood contained the minute rods which he believed to be the cause. Davaine later abandoned this belief because he transmitted the disease with old blood in which he could find no rods. It is now known that this was because the bacilli were in the “spore” form which Davaine did not recognize. He thus missed the definite proof of the bacterial nature of anthrax because he was not familiar with the life history of the organism which was worked out by Koch thirteen years later. In 1865 Villemin repeatedly caused tuberculosis in rabbits by subcutaneous injection of tuberculous material and showed that this disease must be infectious also. In the same year Lord Lister introduced antiseptic methods in surgery. He believed that wound infections were due to microörganisms getting in from the air, the surgeon’s fingers, etc., and without proving this, he used carbolic acid to kill these germs and prevent the infection.