BACTERIA AND SOIL FERTILITY 



as a fish of prey darts through the sea; they were found every- 

 where, although not in large numbers. A second kind was sim- 

 ilar to that marked B (Fig. i) which sometimes spun around in 

 a circle like a top. These were present in larger numbers and 

 sometimes described a path like that shown in C to D (Fig. i.). 



A third kind could not be 



D 







F 



A <r — ^ n distinguished 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 con- 

 tinually 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 

 thousand in a given part of 

 water or saliva mixed with 

 a particle 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 were curved, 

 some straight as shown in F; they lay irregularly and were inter- 

 laced. Since I have previously seen animalcules of this same kind 

 in water, I endeavored to observe whether there was life in them, 

 but in none did I see the smallest movement that might be taken 

 as a sign of life." Some of them he considered traveled with 

 the speed of lightning and even "tore through each other." 



This patient worker, supplied with a microscope of his own 



Fig. i.^ — The first drawings of bacteria by 

 Leeuwenhoek. The dotted line "C-D" 

 indicates movement of the bacteria. 



