136 RESPONSES OF CELLS ON THE BIOLOGICAL LEVEL 



Reproduction of Bacteria and Viruses 



A number of substances which have a very potent effect 

 upon the multiplication of some types of bacteria and 

 plants have also the property of producing at least some 

 of the phenomena which have been mentioned as charac- 

 teristic of the substances which have been classified as 

 mitotic poisons. Amongst the bacteriostatic substances 

 are, for example, the sulphonamides, which have been 

 shown to prevent cell division and cause polyploidy in 

 onion root tips. It may very well be that examination of 

 such cases would assist considerably in understanding 

 the mechanisms which may be involved in mitotic poi- 

 soning. But the analysis of these cases is not likely to be 

 particularly simple. Thus, according to the views de- 

 veloped by Woods and Fildes, the sulphonamides usu- 

 ally exercise their bacteriostatic effect by preventing the 

 utilisation of para-aminobenzoic acid: and Gale has 

 recently suggested that the primary action of penicillin 

 is to prevent the uptake of glutamic acid. The question 

 therefore arises as to whether the action of such sub- 

 stances as mitotic poisons involves the same inhibitions 

 as are supposed to be concerned in bacteriostasis, or 

 whether some other quite different actions are involved 

 when they act as mitotic poisons. 



It is, of course, possible that the bacteriostatic action 

 is, in fact, identical with the action upon mitosis. But it 

 cannot at present be assumed that the phenomena of 



