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Bacilli and other thread-shaped microbes growing very long 

 either in a straight or crooked manner, are called leptothrices,. 

 and when they branch they are called cladothrices. 



1,289 The unit of measurement of bacteria is -nnnrth of. 

 a millimeter, which is equal to 2"5TRro^h> ^ an ^ nc ^> anc ^ ^ * s 

 represented by the letter /*. The length of bacteria usually 

 varies from 2 to 10 /*., and the breadth from -^ to 2 n- The 

 Bacillus anthracis rods are about i /*. in diameter. Yeast 

 cells are about 10 /*. in length. With the help of micro- 

 meters, measuring of bacteria is done at the same time as 

 microscopic observation. The dimensions of a microbe may 

 be also judged by comparison with those of certain microbes 

 whose dimensions are known to the observer. 



1,290. Reproduction. Yeast cells are budding-fungi, 

 whereas bacteria are fission-fungi, and it is better to call all 

 the groups of bacteria, viz. ; micrococci, bacteria and bacilli, 

 by the generic name of Schizomycetes, than by the name of 

 bacteria or bacilli, though it is difficult not to use either of the 

 latter words as the generic name, as in popular language they 

 are all called either bacteria or bacilli. Besides reproduction 

 by gemmation or budding which takes place in the case of 

 yeast fungi, and reproduction by fission which takes place in 

 the case of Schizomycetes, there is another method of repro- 

 duction, vtz., by spore-formation. Yeast fungi usually have 

 four spores formed in each. Bacilli and spirilla usually 

 have several spores in each. Micrococci do not form 

 spores. Some bacilli, e.g., anthrax bacilli, require free access 

 of air and a temperature of between 7oF. to ip5F. for free 

 formation of spores. These are called aerobic germs. Those 

 that thrive only when oxygen is excluded, e.g., the bacillus of 

 tetanus, are called anaerobic germs. Others again thrive 

 either with or without oxygen. These are called facultative 

 germs, their aerobic forms being different from their anaerobic 

 forms. When anaerobic germs are cultivated, they are found 

 to generate mal-odorous gases. 

 PPPP 



