HISTORY OF BACTERIOLOGY 



showed the liveliest and most active motion, moving through 

 the water or saliva as a fish of prey darts through the sea ; 

 they were found everywhere, although not in large numbers. 

 A second kind was similar to that marked B (Fig. i). These 

 sometimes spun around in a' circle like a top, and sometimes 

 described a path like that shown in CD (Fig. i) ; they were 

 present in larger numbers. A third kind could not be dis- 

 tinguished so clearly now they appeared oblong, now 

 quite round. They were so very small that they did not seem 

 larger than the bodies marked E, and, besides, they moved so 

 rapidly that they were continually running into one another ; 

 they looked like a swarm 

 of gnats or flies dancing 

 about together. I had 

 the impression that I was 

 looking at several thou- 

 sands in a given part of 

 the water or saliva mixed 

 with a particle of the ma- 

 terial from the teeth no 

 larger than a grain of sand, 

 even when only one part of 

 the material was added to 

 nine parts of water'or saliva. 

 Further, the greater part 

 of the material consisted of an extraordinary number of rods, 

 of widely different lengths, but of the same diameter. Some 



r c 



FIG. i. Leeuwenhoek's figures. The 

 oldest known figures of bacteria. After 

 Fischer. 



