TEXT-BOOK OF BACTERIOLOGY 



CHAPTER I. 



Classification, Morphology, Biology, Structure, Formation of Groups, 

 Flagella, Powers of Resistance of Spores, Multiplication of Bacteria, 

 Sporulation, Varieties of Spore-formation, Ptomaines, Development 

 of Pigment, Formation of Gases. Production of Odors. 



I. CLASSIFICATION, MORPHOLOGY, BIOLOGY. 



SINCE Anthony Van Leeuwenhoek (1683), with his single lenses, 

 first saw bacteria in mucus of the mouth, and illustrated his dis- 

 covery with excellent drawings, progress in the field of bacteriology 

 has been exceedingly slow until the middle of the present century. 



Even Ehrenberg, who studied the bacteria more closely, knew 

 little else to do with them except to classify them. In fact, he con- 

 sidered them to be the lowest members of the animal kingdom, and 

 thought he saw in them little bladders, which represented stomachs 

 and eggs. 



Ferdinand Cohn, shortly before 1860, showed clearly that they 

 belonged to the vegetable kingdom, remarking that the individuals, 

 grow and divide like plant cells; that they agree with these in 

 structure, and particularly in the manner of fruit-forming, and 

 that they pass through a series of intermediate steps into a higher 

 class that of the colorless algse. 



Cohn also made an attempt to systematize them, but on quite 

 a different basis from that of Ehrenberg. 



Seeing clearly that the necessary arrangement of their various 

 relations to each other in proper classification was still in its in- 

 fancy, he described the outward form only, hoping thereby to bring 

 something like order into this world of apparent chaos. He there- 

 fore distinguished globular, cylinder or rod-shaped, and screw-shaped 

 bacteria, as well as intermediate varieties. Such a classification 

 can, however, only be superficial; for instance, one would, with such 

 a system, have to place the blind-worm with the snakes and the 

 whale with the fishes. But Cohn knew well that he had only done 



