3 3 2 BACTERIOLOGY. 



division lengthen into threads. A thread appears 

 to be first composed of long rods, then of short 

 rods, and lastly of cocci. The iodine reac- 

 tion must be applied to distinguish these forms, 

 especially when the sheath of the threads has 

 a yellow, rust-red, olive-green, or dark-brown 

 coloration. The cocci may grow into rods while 

 still in the sheath, and finally become leptothrix 

 threads, surrounded by a delicate gelatinous 

 sheath, from which the false branching proceeds. 

 Fragments may break off, which are actively 

 motile, and appear as vibrios, spirilla, and spiro- 

 chseta-forms (Fig. 128). They may also occur in 

 zooglcea. 



They are the commonest of all bacteria in 

 both still and running water, in which organic 

 substances are present. They are observed also 

 in the waste water of certain manufactures, such 

 as sugar. Artificially they can be cultivated on 

 infusions -of rotting algse and animal substances, 

 forming on these media small tufts, about i 3 /x, 

 and floating masses. 



Cladothrix Fcersteri (Streptothrix Forsteri, 

 Cohn). Cocci, rod-forms, and leptothrix-threads. 

 The threads are twisted in irregular spirals, 

 and branch sparingly and irregularly. Screw- 

 forms are produced by the threads breaking up 

 into small pieces. They occur in the lachrymal 

 canals of the human eye, in the form of closely 

 felted masses. 



