BESISTANCE OF SPORES. 53 



samples of 2 c.c. each are removed and placed in reagent- 

 glasses of equal thinness, while in a sixth one are placed 

 2 c.c. of water and a thermometer. All six glasses are 

 now plunged in a large water-bath containing boiling 

 water, and after two minutes the thermometer in the con- 

 trol tube reaches a maximum temperature (99° to 100°). 

 Two minutes later one removes the first sample, four min- 

 utes later the second, etc., cools them rapidly in cold 

 water, and utilizes 1 c.c. and -J c.c. of each sample in the 

 preparation of plates. For further details, see Stephanidis, 

 A. H. XXXV, 1. 



The varying resistance of apparently identical anthrax 

 spores ia oi great practical importance: (1) in disinfection 

 experiments, which should be carried out with spores of 

 known resistance; (2) in differential diagnosis, as it indi- 

 cates how very careful one must be in placing dependence 

 upon a slight diii'erence in the resistance of spores in de- 

 termining two species. 



Very extraordinary is the resistance of many varieties occurring in 

 hay and soil. Christen fonnd, for example (C. B. xvii, p. 498), that 

 with compressed steam the resisting spores in soil were killed — 

 At 100° in more than 16 hours. 

 " 105°-110° in 2 to 4 hours. 



" 115° " 30 to 60 minutes. 



" 12.5°-130° " 5 minutes and longer. 



" 135° " 1 to 5 minutes. 



" 140° " 1 minute. 



The apparatus employed brought the objects to the desired elevation 

 of temperature very quickly. 



Also against chemical agents spores are very resistant; 

 thus, anthrax spores (v. Esmarch, I. c) ves\nt5'/o carbolic 

 acid for at least two days, and in many cases as long as 

 forty days. Very resistant anthrax spores withstood a 1% 

 aqueous sublimate solution for three days, but the viru- 

 lence is lost in twenty hours. Such experiments are best 

 made with thin suspensions of spores in water, to which 

 the disinfectant is added, just as was pointed out above for 

 testing the action of antiseptics upon bacteria (p. 38). 



In testing the resistance of spores to gases, they are best 

 dried upon pieces of glass, and the gas allowed to operate 

 in a dry and also in a moist chamber (compare p. 41). 



Spores are also less injured by light than bacilli are. As 



