1 90 BACTERIOLOGY. 



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. 



Sphaerotilus natans. Cells 4 9 JJL long, 

 3 p. thick, united in a gelatinous sheath to 

 form threads. The cells comprise rods and 

 cocci-forms ; the cocci are set free, and develop 

 into rods, which again form threads. In the 

 last a false branching has been observed. The 

 plasma of the cells breaks up into minute, 

 strongly refractive portions, which develop into 

 round spores, at first of a red, and afterwards 

 a brown colour. They occur in stagnant and 

 flowing water contaminated with organic matter, 

 and form floating flakes of a white, yellow, rust- 

 red, or a yellow-brown colour. 



