CHAPTEE II. 



MORPHOLOGY AND PHYSIOLOGY OF BACTERIA. 



Bacteria may be considered as minute vegetable cells destitute of 

 nuclei. They are distinguished from animal cells by being able to 

 derive their nitrogen from ammonia compounds, and they differ 

 from the higher vegetable cells in being unable to spUt up carbonic 

 acid into its elements, owing to the absence of chlorophyll. Von 

 Engelmann and Van Tieghem include among the bacteria certain 

 organisms, named by them Bacterium chlorinum, Bacterium ^-iride, 

 and Bacillus ^-irens, which are coloured green by this substance, but 

 it is quite possible that they may be Algae, and further researches 

 are required before any conclusions are definitely arrived at as to 

 the exact place these particular organisms occupy in the vegetable 

 kingdom. 



Composition. — For our knowledge of the chemical composition 

 ■of bacteria we are chiefly indebted to Nencki. Their constituents 

 are found on analysis to vary slightly, according to whether the 

 bacteria are in zoolgoea or in the active state. In the latter condition 

 they are said to consist of 83'42 per cent, of water. In one hundred 

 parts of the dried constituents there are the following : — 



A nitrogenous body ..... 84*20 



Fat . 6-04 



Ash 4-72 



Undetermined substances .... 5-04 



This nitrogenous body is called myco-protein, and consists of 



Carbon 52-32 



Hydrogen 755 



Nitrogen 14-75 



but no sulphur or phosphorus. 



The nitrogenous body appears to vary in different species, for 

 in Bacillus anthracis a substance has been obtained which does not 



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