CHAPTER VIII. 

 PHYSIOLOGY OF MICRO-ORGANISMS. 



Relations of Morphology and Physiology. In morphological 

 study observations are restricted to the relationship of various 

 elements at a given time, facts relating to form and structure. 

 From the physiological viewpoint one is more interested in the 

 sequence of events and the relation of cause and effect. The 

 possible suggestion that these two methods of study are independ- 

 ent or mutually exclusive would be most unfortunate and is really 

 very fallacious. The sequence of events may often best be ascer- 

 tained by a series of morphological observations of a microbe 

 undergoing change of form, and certainly the form and structure 

 of a living organism at a given time may be properly regarded as 

 an expression and result of previous physiological activity as well 

 the most essential element in its potentiality for future activity. 

 All must agree that difference in behavior, that is, reaction to a 

 definite environmental change, is really associated with a difference 

 in structure of the living organism. The important difficulty 

 lies in the fact that the morphological or structural difference 

 with which this difference in reaction is correlated, may not be 

 capable of direct observation by any known method and may be 

 ascertainable only by means of the physiological test. On the 

 other hand the method of experimental physiology involves the 

 factor of environment, small and unmeasured differences in which 

 may grossly influence the resulting phenomenon and lead to erro- 

 eous conclusions. Furthermore, the experimental conditions and 

 the method of physiological observations may be wholly lacking 

 in adaptation to potentialities of the organisms under observation. 

 When properly employed, however, the method of experimental 

 physiology yields valuable knowledge obtainable in no other way, 



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