38 BULLETIN OF TIIE 



stances, furnish us with important information concerning the 

 quality of the air, hut great caution is necessary in dealing with 

 this principle of examination. 



A scries of investigations upon the effects of various soils upon 

 ordinary Bewage has been carried on under the direction of Prof. 

 Pumpelly, of the United States Geological Survey, assisted by Prof. 

 Smythe. The preliminary experiments related to the removal of 

 living organisms from air and fluids by passing these through filters 

 of various kinds, and then testing their effects upon solutions con- 

 taining- organic matter and susceptible of fermentative or putre- 

 factive changes. A very large number of such solutions have been 

 prepared and preserved under various conditions, and in no case 

 has anything like fermentation or the development of the lower or- 

 ganisms been observed, unless under circumstances where the lower 

 organisms could be introduced from without, thus giving strong 

 negative evidence against the theory of spontaneous generation. 

 The filtration of air from such germs was found to be a compara- 

 tively easy matter. Passing it through an inch of fine saud de- 

 prived it of the power of producing fermentative changes. On the 

 other hand, the removal of bacteroidal organisms from water was 

 much more difficult, filtration through many feet of fine sand being 

 insufficient to effect it. The results reported by Wernich are con- 

 firmed, viz., that air passing over putrefying fluids or moist putre- 

 fying surfaces does not take up organisms therefrom, nor does it 

 become contaminated by passing over dried bacteria films on smooth 

 compact surfaces such as glass or iron. From woven stuffs, how- 

 ever, it is readily contaminated, and wherever there is dust there is 

 danger. 



The results obtained by Dr. Bigelow in attempting to destroy the 

 vitality of dried bacteria films by means of gaseous disinfectants 

 were then mentioned. It is found that time is an important element 

 in the matter, and that long exposures are necessary to secure com- 

 plete destruction of vitality of such organisms. This may explain 

 the failures to disinfect the Plymouth and the Excelsior by gaseous 

 disinfectants. 



Drs. H. C. Wood and H. F. Fremont have made a number of 

 experiments on the inoculation of diphtheria on the lower animals 

 with negative results. The theory of Oertel that this disease is due 

 to specific bacteria is not confirmed by their observations. They 

 state that their results seem to indicate that the contageous material 



