CONCLUSIONS 173 



dence, so far, has shown that enzymes react more slowly 

 than the reproduction mechanisms. 



11. Growth retardation by antiseptics is not always due 

 to the same reaction. Here too, as a rule, the enzymes 

 suffer less than the mechanisms of synthesis and cell di- 

 vision. But there is more variety in the mode of attack 

 than with disinfectants. The most common effect is a 

 decrease of the growth rate, probably from partial inacti- 

 vation of the catalysts which bring about synthesis. The 

 sulfonamides are different from all other antiseptics, for 

 they do not affect resting cells. They interfere only with 

 the third or fourth generation of growing cells, and the 

 interference can be avoided completely by addition of 

 p-amino benzoic acid. This suggests that growth is not 

 inhibited because the sulfonamide reacts with some essen- 

 tial cell protein, but because it becomes part of the cell 

 structure which then fails to function. 



12. The retardation by dyes is quite certainly due to 

 an abnormal oxidation-reduction potential, and if the 

 cells are present in sufficient numbers, they can readjust 

 the potential and can then multiply completely unre- 

 stricted. 



13. An investigation of the relation between the acidity 

 and the antiseptic power of organic acids and sulfur diox- 

 ide has shown that the undissociated acid molecules are 

 the. real inhibitory factor, probably because they get into 

 the cell more readily than the ions. 



14. The picture of death and of growth inhibition is 

 by no means perfectly clear, and it cannot be clear as 

 long as we have no perfect understanding of the mechan- 

 isms upon which life depends. But by varying the con- 

 dition of death, by varying the species under test, and by 

 applying quantitative methods, our conceptions of the 

 death of the cell are becoming more definite, and ulti- 

 mately this study will not only explain the mechanism of 

 death, but will permit important conclusions about the 

 unknown mechanism of life. 



