THE BACTERIA AND VIRUSES 



345 



cytoplasm differs from that of higher plants in its strong affinity for basic 

 stains, in which it resembles chromatin. When this basophil cytoplasm is 

 removed bv acid hydrolysis, it is, however, possible to show that true 

 chromatin occurs in granules, which divide when the cell divides and to 





Fig. 333. — Azotobacter chroococcum. Stained to 

 show nuclear bodies in cells. 



which the term nucleus may be applied, though there is nothing like a fully 

 organized nucleus (Fig. 333). 



Bacteria which are motile possess flagella (Fig. 334), filaments of extreme 

 tenuitv which are in some species attached all over the surface of the cell, 



^'^'^ ■ 



■ .J 



Fig. 334. — Salmonella typhosa. Stained to show flagella. 

 ( By courtesy of the General Biological Supply House Inc . , Chicago .) 



and in others are confined to one or to both ends. Even in motile forms 

 they are usually produced only by young cells and may be dropped off if 

 multiplication becomes slow and the cells become senescent. They are 

 presumably protoplasmic, as they show active gyratory movements and 

 by their aid the cells can travel at surprising speeds. Instances are known 

 of Bacteria moving 100 times their own length in one second, which is 

 analogous to a speed of 400 miles per hour for man ! 

 12 A 



