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CLINICAL BACTERIOLOGY. 



PART I. 



L MORPHOLOGY AND BIOLOGY OF BACTERIA* 



THE minute forms of life constituting in largest part the 

 exciting agents of the infectious diseases occupy the lowest 

 level in the vegetable kingdom. They are designated bac- 

 teria or fission-fungi. The latter term is, however, not well 

 chosen. The botanic conception of fungi includes those 

 lower forms of vegetable life that are without the coloring- 

 matter of leaves (chlorophyl) or similar coloring-matters 

 (chromophyls). There are not a few bacteria, however, 

 that are capable of generating such coloring-matters, and, 

 thus, also of decomposing carbon dioxid and its combi- 

 nations, and utilizing the products of this activity. There 

 is, thus, no justification for the term fission-fungi, and it is, 

 therefore, preferable to designate the minute forms of life 

 under consideration as bacteria. 



There is as yet no strictly scientific, natural classification 

 of bacteria. For the present the adoption of an artificial 

 system, based upon such physical features as the size, the 

 shape, and the arrangement of the bacteria, must suffice 

 (F. Cohn). (See Figs. I, 2, 3.) Three main divisions are 

 recognized: (i) Spheric bacteria (cocci, micrococci, coc- 

 caceae) ; these are spheric cells. (2) Rod-shaped bacteria 

 (bacilli, bacteriaceae) ; these are rod-like, cylindric cells. 

 (3) Spiral bacteria (vibrios, spirilla, spirillaceae) ; these 

 are twisted in both the horizontal and the vertical direc- 

 tion, and are, thus, comparable to the windings of a screw 

 or of a corkscrew. 



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