CHAPTER VIII. 



GENERAL MORPHOLOGY AND PHYSIOLOGY. 



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 toij^unable to 

 split 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 viride, and Bacillus virens^ which are 

 coloured green by this substance ; but further 

 researches are required before any conclusions are 

 definitely arrived at as to the place of these parti- 

 cular organisms in the vegetable kingdom. It is 

 quite possible that they may be Algae, and they 

 will, therefore, find no place in the classification 

 which will be here adopted. 



Chemical composition. For our knowledge 

 of the composition of bacteria we are chiefly in- 

 debted to Nencki. Their constituents are found on 



