HARMFUL BACTERIA 65 



but No. 4, the one in which was put the corrosive 

 sublimate. This is a poison to human beings when 

 taken internally. 



No. i is open to air and dust and in time will be- 

 come sour or undergo fermentation. If left long 

 enough the milk may putrify. 



No 2 is closed to dust but not to air. However, 

 no pains was taken to free the bottle, or plug from the 

 dust which was on them or in the contents, so in time 

 this will become, sour. 



No. 3 has all the conditions of No. i except warmth, 

 which is favorable, and light, which to some dust 

 plants is unfavorable. It should not spoil or sour as 

 quickly as No. i. 



No. 4 has been treated by a chemical which is poi- 

 sonous and should kill the dust-plants present. This, 

 if strong enough to kill, is a disinfectant. If only 

 strong enough to prevent or retard growth for a while 

 it would be an antiseptic. There should be no change 

 in No. 4. 



No. 5 will have been sterilized, that is, all life within intermittent 

 liquid, or bottle, killed by the steaming process. 8teriliz tion 

 The first steaming is expected to kill all the growing 

 or vegetative forms then present. It may not be enough 

 to kill any spores that are there. These will be en- 

 couraged to grow by the greater heat, but on the sec- 

 ond day they will have developed into the ordinary 

 growing form and the steaming should kill them. 

 That sterilization may be assured and any possibly 



