TOXICOLOGY AND PHARMACOLOGY 397 



If the disinfectant were a firm combination with the microorganism 

 it would be difficult to explain how the germ could multiply again 

 when removed from the disinfectant solution. This is readily under- 

 stood if we assume that the union between microorganism and dis- 

 infectant is an adsorption. In that case the disinfectant will pass 

 into the absolutely indifferent solvent so that the microorganism 

 having become free again (from the disinfectant) is in a condition to 

 continue its development. 



A few examples will explain the foregoing. R. KOCH performed 

 certain experiments in the following way: he dried germs on silk 

 threads and subjected them for a given time to a disinfectant solu- 

 tion; after this he placed them in nutrient bouillon or in gelatin; 

 if the germs developed, he considered that the disinfectant was 

 active; if they did not, that it was inactive. In this way R. KOCH 

 subjected anthrax spores for two days to 5 per cent carbolic acid and 

 found that afterwards they did not develop in gelatin. B. RIEDEL, 

 in the Imperial Health Office, found that, even after 14 days of im- 

 mersion in 5 per cent carbolic acid, the germination of anthrax spores 

 was not inhibited if the silk threads were first washed with water 

 and then placed in fluid gelatin; the gelatin and silk threads were 

 thoroughly mixed by prolonged agitation of the test tube. 



According to R. KOCH, a single immersion of anthrax spores in 

 1 : 5000 sublimate solution suffices to destroy them. J. GEPPERT* 

 found that the same concentration acting four seconds longer, on 

 one trial, produced their death and on another did not. Among 

 eountless experiments on this point we shall mention those of EISEN- 

 BERG and OKOLSKA because of the method they employed. 



They mixed uniform quantities of disinfectant and bacteria, some- 

 times adding the entire quantity of bacteria at once, and sometimes 

 in fractions. If the phenomenon is reversible, the results in both 

 cases should be the same; if it is irreversible there should be a point 

 in the fractioning experiment when the disinfection should prove less 

 satisfactory. As was to be expected from other considerations, the 

 action of phenol proved to be reversible and that of KMnO 4 and 

 HgCl 2 to be partly irreversible (in these instances the time of action 

 was an important factor). 



Numerous experiments have been performed in an attempt to test 

 quantitatively the views given here; the results actually satisfy the 

 hypothesis in some instances. An exact agreement between obser- 

 vation and calculation is not to be expected because in disinfection 

 adsorption is not the only factor, though it is chiefly accountable 

 for the action of the disinfectant on the microorganism (lipoid solu- 

 bility, modification of protoplasm, etc.). 



