THE BACTERIAL CELL 



the recognition of the existence in the bacterial cell of a number of 

 structures which, although often ill defined in nature and function, 

 obviously express a morphological complexity parallel to the bio- 

 chemical complexity of all known forms of life. Utilization of the 

 classical methods of cytology soon revealed, for example, the existence 

 in bacteria of flagella, spores, different kinds of membranes and capsules 

 etc., which give to each bacterial type a fairly characteristic morpho- 

 logical individuality (12). Little by little, bacteriological staining 

 techniques are gaining the dignity of cytochemical reactions and give 

 chemical definition to the cellular objects which they reveal; the more 

 skillful utilization of Feulgen's reagent for instance, permits the identi- 

 fication among the other basophilic constituents of the bacterial cell of 

 discrete bodies rich in desoxyribonucleic acid which are almost cer- 

 tainly the equivalent of the vesicular nucleus in larger cells (12,19). 

 Photography in the ultraviolet and electron microscopy have per- 

 mitted the optical resolution of cellular structures — intracellular 

 granules, membranes, individual components of flagella, etc. — which 

 are below the limit of resolution by ordinary microscopy. These 

 classical cytological techniques aim at the direct visualization of the 

 constituents of the cell. On the other hand, the analysis of the re- 

 sponse of the cell to the effect of certain reagents and procedures pro- 

 vides an indirect approach to cytological problems, by suggesting the 

 existence and often the chemical nature of important cellular com- 

 ponents which cannot be seen by any of the known methods of micros- 

 copy. Interestingly enough, it is the study of pathogenic bacteria 

 which has been the most fruitful from the point of view of this indirect 

 approach to cytology. 



In order to analyze the host-parasite relationship, the student 

 of infection must concern himself with those structures and products 

 of bacteria — the cellular antigens and toxins — which affect the course 

 of the infectious process and against which are directed the reactions 

 of immunity. Similarly, the attempts to understand the mode of 

 action of antiseptics on bacteria led to the study of the structures 

 through which antiseptic agent and susceptible cell come in contact. 

 Thus, many constituents of the bacterial cell have been recognized 

 first by biological reactions; and the analysis of the phenomena of 

 infection, immunity, and chemotherapy has provided important in- 

 formation concerning the biochemical architecture of bacteria. Paul 



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