INTRODUCTION. HISTORY.-The microscope was invented about the latter part of the sixteenth century; and soon after, by its aid, minute organisms were found in decomposing substances. Kircher, in 1646, suggested that diseases might be due to similar organisms; but the means at his disposal were insufficient to enable him to prove his theories. Anthony Van Leuwenhoeck, of Delft, Holland (1680 to 1723), so improved the instrument that he was enabled thereby to discover micro-organisms in vegetable infusion, saliva, fecal matter, and scrapings from the teeth. He distinguished several varieties, showed them to have the power of locomotion, and compared them in size with various grains of definite measurement. It was a great service that this 'Dutch naturalist" rendered the world; and he can rightly be called the "father of microscopy." Various theories were then formulated by physicians to connect the origin of different diseases with bacteria; but no proofs of the connection could be obtained. Andry, in 1701, called bacteria worms. Müller, of Copenhagen, in 1786, made a classification composed of two main divisions-monas and vibrio; and with the aid of the compound microscope was better able to describe them. Ehrenberg, in 1833, with still better instruments, divided bacteria into four orders: bacterium, vibrio, spirillum, and spirochete. It was not until 1863 that any positive advance was made in connecting bacteria with disease. Rayer and Davaine had in 1850 |