CHAPTER I 



INTRODUCTION: MORPHOLOGY 



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Form, Size, and Structure of the Bacterial Cell, Cell-membrane, 



and Cell-contents. 



THE first historically recorded discovery of bacteria was made more 

 than two hundred years ago by Anton van Leeuwenhoek, the Dutch 

 naturalist and pioneer in the world of the infinitely little. Exploring those 

 then untravelled regions with home-made lenses of wonderful efficacy, he 

 found in the saliva of the human mouth 

 minute organisms to which he gave the 

 name of animalcula on account of their 

 power of movement. 



In the description (1) and in the figures 

 he gives (reproduced in facsimile in Fig. i), 

 curved and straight forms and long and 

 short rods are plainly recognizable. They 

 constitute the earliest reliable record of 

 bacteria, the study of which in later times 

 has revolutionized medicine and expanded 

 into a new science. From the year 1683 

 Leeuwenhoek 's observations stood alone 

 until, a century later, the Danish savant 

 Miiller made further investigations on bac- 

 teria. He classified them with the infusoria 

 and gave them names that are now familiar 

 to us all, Vibrio^ Spirillum, and Bacillus. 



In 1838 Ehrenberg described in his great work on infusoria a large number 

 of bacterial forms, ranking them with his group Vibrionia, and from this 

 time forward the bacteria have never again drifted entirely out of sight. 



It was not, however, until about the seventh decade of this century that 



FISCHER 1'. 



FlG. I. Oldest known figures ot genuine 

 bacteria (bacteria of the mouth) from Leeu- 

 wenhoek. A and f represent Bacillus hue- 

 calls -niaxintus. B is perhaps Vibrio 

 buccalis ; its movements were followed by 

 Leeuwenhoek from Clo D. E\sa. species of 

 coccus, and G, no doubt, a Spirillum spiiti- 

 gctnini (compare with FlG. 26). 



