36 PATHOGENIC BACTERIA. 



of these is much less clear. It seems to be an effort to 

 convert the entire microbe into a permanent form. This 

 process is observed particularly in the micrococci, where 

 the substance of a cell is said to break up into segments, 

 each of which becomes a resisting body fruitful in prop- 

 agating its species. Of the arthrospores little has, so 

 far, been learned. It is not improbable that among the 

 micrococci, and also among some of the smaller bacilli 

 in whom no spores have been observed, the maintenance 

 of the species when conditions of life become unfavor- 

 able is due to the assumption of a permanent form by 

 some of the individuals, without the formation of any 

 spore-like bodies. This is at present largely a matter of 

 conjecture, but the indications pointing in that direction 

 are numerous. 



It is believed by Frankel and others that sporulation 

 in the bacteria is not a sign of the exhaustion of nutri- 

 tion, but a sign of the vital perfection of the organism. 

 These observers regard spore-formation as analogous to 

 the flowering of higher plants, which takes place only 

 when the conditions and development are best. 



Morphology. The morphology of the bacteria is quite 

 varied. Three principal forms, however, exist, from which 

 the others seem to be but variations. 



The most simple appear as minute spheres, and from 



g 







FIG. 2. Diagram illustrating the morphology of the cocci : a, coccus or 

 micrococcus ; 6, diplococcus ; t, d, streptococci ; e, f, tetragenococci or meris- 

 mopedia ; g, h, modes of division of cocci ; i, sarcina ; j, coccus with flagella ; 

 k> staphylococci. 



their fancied resemblance to little berries are called cocci 

 or micrococci (Fig. 2, a). When the bacteria of this form 



