194 TEXT-BOOK OF BACTERIOLOGY. 



lucid, and show perfectly regular screw-like windings. The length 

 varies extremely, according to the more or less favorable conditions 

 of development, so that one may sometimes find spirilla of only 

 three or four windings, sometimes of more than forty. They are 

 very motile, and the shorter ones especially shoot quickly 

 across the field with a twisting or boring motion, while the larger 

 ones gradually grow less active, and at last quite lose their power 

 of locomotion. The organ of locomotion is easily seen by the aid of 

 Loffler's process as a wavy flagellum at either end of the screws. 



The spirillum multiplies by means of transverse segmentation. 

 A thread breaks up into several more or less equal portions, which 

 again in their turn grow out into individuals of greater length. 



This micro-organism has a marked inclination to produce in- 

 volution forms. Older cultures in particular contain hardly a sin- 

 gle individual which would fully answer to the above description. 

 One sees only quite short threads often curiously dilated, or thick- 

 ened at the end, which do not recover the normal form till they 

 are transplanted to a fresh food medium. 



The investigations of v. Esmarch leave it undecided whether 

 the spirillum forms spores or not. In the unstained preparation 

 one often notices that a number of screws have bright, sharply- 

 defined spots in their interior, and these when treated with anilin 

 stains, even if the latter are warmed and allowed a long time to 

 act, remain as unstained gaps. Such spirilla possess a very con- 

 siderable power of resistance against desiccation, and when pre- 

 served on silk threads are capable of propagation after eight weeks. 

 On the other hand, they perish from high temperatures above 50° 

 C. at once, and as a special staining of the already-mentioned spots 

 in the manner of double spore- staining has hitherto always failed, 

 we must reserve our judgment as to the sporulation or non-sporu- 

 lation of the spirilla until further investigators have thrown more 

 light on the question. 



The spirillum thrives best at temperatures between 16° and 

 about 40° C, while 37° suits it best. Yet tl;ie capacity of sponta- 

 neous movement can only be permanently retained at low temper- 

 atures. If the access of oxygen is restricted, moderate growth 

 still continues. 



The growth of the spirillum is extremely slow and tardy on all 

 our food media. On the gelatin plate, for instance, the commence- 

 ment of its development is not recognizable till after five days, and 

 weeks pass before colonies visible to the naked eye are formed. 

 When they appear they are seen as grayish- red rounded heaps as 

 large as a pin's head, which never liquefy the gelatin and which ap- 



