36 



PATHOGENIC BACTERIA. 



been speaking, there are arthrospores. The formation 

 of these is much less clear. It seems to be the conver- 

 sion of the entire microbe into a permanent form. This 

 process is observed particularly in the micrococci, where 

 in the chains or groups certain individuals become en- 

 larged beyond the normal, and surrounded by a capsule. 

 Hiippe, who has paid particular attention to the arthro- 

 spores, believes that they have resisting powers far 

 beyond those possessed by the bacteria themselves. 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 unfavorable is due to the as- 

 sumption of a permanent form by some of the individ- 

 uals, 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 

 their fancied resemblance to little berries are called cocci 

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

 multiply by fission the resulting two organisms not 

 infrequently remain attached to each other, producing 

 what is called a dipiococcus (Fig. 2, b). The diplococci 

 sometimes consist of two perfect spheres, but more often 

 show a flattening of the contiguous surfaces, which are 

 not in absolute apposition (Fig. 2, g). In a few cases, as 

 the gonococcus, the approximated surfaces are slightly 

 concave, causing the organism to somewhat resemble the 





