BAGTEEIOLOGY 



CHAPTEE I 



GENERAL MORPHOLOGY AND BIOLOGY OF MICRO-ORGANISMS 



Introductory. — Varieties of micro-organisms. — Within and 

 without the human body there exist countless organisms of 

 microscopic minuteness, micro-organisms, which, alighting 

 upon the surface, may effect an entrance in various ways 

 into the interior ; they belong partly to the vegetable, 

 partly to the animal kingdom, and have the property of 

 developing on animal and vegetable bodies. According 

 as they are capable of growth upon dead substances or 

 living matter, we distinguish respectively saprophytes and 

 parasites ; the latter of which are subdivided into obligate 

 and facultative parasites — -the obligate or strict parasites 

 being those which grow exclusively in the living body and 

 perish apart from it, whereas the facultative parasites have 

 the power of adapting themselves to altered conditions of life, 

 and of flourishing externally as well as internally. With fur- 

 ther reference to their relation to the human or animal frame 

 we speak also of ectogenous micro-organisms, which occur 

 outside the body, of endogenous, which exist in its interior, 

 and of amhigenous, which are capable of life either within 

 or without. Again, the majority are unable to live without 

 oxygen, and these are termed aerobes ; but a large number 



B 



