TESTS OF DISINFECTION 39 



organisms upon which experiments have been made, 

 or of harmless species of the same class, are efficient 

 for the destruction of all, in the absence of spores. 

 There is, it is true, within certain limits, a difference 

 in the resisting power of different organisms of this 

 class to chemical agents. This is not, however, suffi- 

 ciently marked to prevent the general statement that 

 a disinfectant for one is a disinfectant for all, in the 

 absence of spores. 



The last clause of the above statement calls for an 

 explanation, and certain details with reference to the 

 mode of reproduction of disease germs. All of the 

 bacteria multiply by binary division ; that is, one in- 

 dividual divides into two, and each member of the 

 pair again into two, and so on. The spherical bac- 

 teria, known as micrococci, multiply only in this way, 

 but some of the rod-shaped bacteria, or bacilli, also 

 form spores. These spores correspond with the seeds 

 of higher plants. They are highly refractive, oval or 

 spherical bodies, which, under certain circumstances, 

 make their appearance in the interior of the rods, 

 which cease to multiply by binary division when spore 

 formation has taken place. The point of special in- 

 terest with reference to these spores is, that they have 

 a resisting power to heat, and to the action of chem- 

 ical disinfectants, far beyond that which is possessed 

 by micrococci, or by bacilli without spores. The 



