ON THE DESTRUCTION OF INFECTIOUS GERMS. 829 



clothing, pieces of different clothing materials were impregnated with 

 strong putrefying and bacteria-bearing fluids, then dried slowly, and 

 kept for a long time without protection against external influences. 

 "Whenever the smallest piece of one of these materials was put into a 

 suitable fluid, the perturbation invariably took place which is the sure 

 sign of the active multiplication of bacteria. Clothing which had not 

 been impregnated did not excite this perturbation, or only in an insig- 

 nificant degree. Specimens of the defiled clothing which were placed 

 in a similar solution after they had been exposed for five minutes to 

 a temperature of from 125 to 150 C, or for one or two minutes to a 

 higher temperature, produced no change. The capacity of the bacteria 

 to resist heat varies widely among the different species, and appears 

 to depend largely on the faculty of developing spores. The individ- 

 uals are killed, but the spores remain vital. The increase of any one 

 kind is limited by the presence of other kinds, with which a struggle 

 for existence has to be maintained. 



No increase of bacteria takes place without the presence of a suit- 

 able substance to support them. The most favorable of non-nitro- 

 geneous substances is sugar ; among nitrogeneous substances the most 

 favorable are the albuminoids ; among mineral matters, potash, phos- 

 phorus, magnesia, and sulphur. If the supporting substance, even 

 though it is needed in only a minute quantity, is consumed, or if it is 

 present in great excess, a pause in the development, but not the death 

 of the bacteria, takes place. A similar effect is produced by taking 

 away the water, but, when the water is restored, an increase of life 

 again takes place. 



The practical object of disinfection should be to go beyond se- 

 curing a suspension of animation of the bacteria, and to seek to destroy 

 the vitality of the spores. Neither years of dryness, nor months of 

 exposure in foul water, nor repeated drying and moistening, will injure 

 the fertility of these germs. 



An excess of water produces a similar effect with desiccation upon 

 the vital conditions of the bacteria. A great dilution of the support- 

 ing fluid by the infusion of pure water will in a short time produce a 

 suspension of the process of decomposition. Privation of light has no 

 effect. The operation of electricity has not been enough observed to 

 justify the drawing of any conclusion. The effect of the privation 

 of air has not been fully determined. It was once thought that the 

 development of bacteria could be hindered by the removal of oxygen, 

 but this is doubtful. Oxygen greatly speeds the development, but it 

 can take place without it. Bacteria are not developed in nitrogen, 

 hydrogen, carbonic oxide, carbonic acid, nitrous oxide, and illuminat- 

 ing gas. 



The substances which are fatal to the life of the bacteria next de- 

 mand attention. Among these, the concentrated mineral acids, iodine, 

 bromine, chlorine, the sulphates of copper and zinc, corrosive subli- 



