ANTISEPTICS AND DISINFECTANTS, 169 
These different methods give results which cannot be directly 
compared one with another, for to obtain corresponding results we 
must have identical conditions. 
Test by Inoculation into Susceptible Animals.—In testing the 
action of disinfectants upon anthrax spores and other infectious dis- 
ease germs, we may inoculate the microérganisms, after exposure to 
the disinfectant, into a susceptible animal. This method was adopted 
by the writer in a series of experiments in 1881, but he has not since 
employed it, for reasons set forth in his paper giving an account of 
these experiments. 
“First. The test organism may be modified as regards repro- 
ductive activity without being killed; and in this case a modified form 
of disease may result from the inoculation, of so mild a character as 
to escape observation. Second. An animal which has suffered this 
modified form of the disease enjoys protection, more or less perfect, 
from future attacks, and if used for a subsequent experiment may, 
by its immunity from the effects of the pathogenic test organism, 
give rise to the mistaken assumption that this had been destroyed 
by the action of the germicidal agent to which it had been sub- 
jected.”? 
In experiments to determine the value of an agent as a disinfec- 
tant, no matter by what method, the following conditions, which in- 
fluence the result, should be kept in view : 
(a) The difference in vital resisting power of different species 
of bacteria. As arule, the pathogenic species have rather less re- 
sisting power than the common saprophytes, and the micrococci 
have greater resisting power than many of the bacilli. The differ- 
ence in the vital resisting power of some of the best known patho- 
genic species is shown in the following table, which we have made 
up from determinations made by Boer—cultures in bouillon twenty- 
four hours old ; time of exposure, two hours. 
| | Chloride of Nitrate 
Hydrochloric Caustic Gold and of Carbolic 
| Acid. Soda. Sodium. Silver. Acid. 
Anthrax bacillus....... 1: 1100 1 +450 1:8000 1: 20000 1: 300 
Diphtheria bacillus..... 1:70) 1:3800 1 :1000 1 :2500 1:3800 
Glanders bacillus ..... 1: 200 1: 150 1:400 1: 4000 1 :3800 
Typhoid bacillus...... 1 :300 1:190 1 :500 1: 4000 1: 200 
Cholera spirillum...... 1: 14850 1:150 1: 1000 1 :4000 1:400 
(b) The presence or absence of spores. The reproductive ele- 
ments known as spores have a far greater resisting power to chemi- 
cal agents, as well as to heat, than have the vegetative cells. In 
1 Quoted from article on ‘‘ Germicides and Disinfectants,” in ‘‘ Bacteria,” p. 212. 
