SPORES— PRODUCTS OF METABOLISM 5 



occupy one end, as in the Tetanus bacillus, the cells show 

 some resemblance to a drum-stick. 



Formation of spores in the interior of the mother-cell 

 is described as proper or endogenous, while arthrogenous is 

 the term applied to that which takes place when single 

 portions separate from the cell and develop gradually into 

 independent individuals {arthrospores). 



Bacteria require for their growth a certain amount of 

 moisture, many of them' speedily perishing if dried. 



Products of metabolism in bacteria, — The biological 

 properties of bacteria are, next to their morphological 

 peculiarities, of special importance. 



A large number of micro-organisms have the property 

 of generating colouring matter, though not chlorophyll. 

 The bacteria are themselves colourless and transparent, 

 and the pigment is merely formed as a product of their 

 metabolism, especially under the influence of light. 



Many bacteria throw off odorous products, and some 

 anaerobic micro-organisms generate very foul putrefactive 

 gases (ammonia, sulphuretted hydrogen, scatol, &c.) . The 

 bacillus of Asiatic cholera exhales a pleasantly aromatic 

 odour, and the Bacillus prodigiosiis a smell resembling that 

 of trimethylamine. 



Micro-organisms have also the property of producing 

 changes in the medium on which they are cultivated by the 

 products of their metabolism, so that albuminoid sub- 

 stances are peptonised by some of them and gelatine 

 liquefied. Many have the faculty of resolving organic 

 bodies into their simplest elements ; but some possess 

 the power of forming nitrates by the conversion of am- 

 monia into nitrous and nitric acids. Certain microbes 

 break up the chemical combination of albuminoid bodies, 

 causing putrefaction, while others induce fermentation ; 

 and a small number, again, have the property of becpming 



