318 



BULLETIN, No. 161 



[November, 



RESULTS 



The results are given in Table IT. These are the 

 average results from two testings of all organisms 

 used. Some other tests were made, but the re- 

 sults are only slightly different from the average of these two 

 complete series. In each of these two series the organisms were 

 all tested at the same time and under the same conditions, with 

 the exception that the cultures were grown upon different media, 

 as noted above. This may have made some difference in the 

 results. The tubercle bacilli were grown upon glycerine egg media 

 for approximately three weeks, while B. violaceus, for instance, 

 was grown in broth for 24 hours at 30 C. The tubercle bacilli 

 were emulsified in 0.8 percent salt solution and transferred to the 

 sterile paper slips, while the B. violaceus were transferred directly 

 from the broth to the slips. It may be that at least part of the 

 difference in the length of time required to kill these organisms 

 by desiccation is due to this difference of growth and age of the 

 cultyres. 



It is seen that a very little longer time is required to kill the 

 tubercle bacilli than other nonspore-bearing organism ; and this 

 slight difference may readily be produced by the protection of the 

 glycerine clinging to these organisms from the culture media, or 

 more likely the protection offered by the presence of clumps of 

 tubercle bacilli. It is almost impossible to eliminate clumps from 

 an emulsion of tubercle bacilli, while other organisms repeatedly 

 grown in broth may be well separated. 



The tubercle bacilli, therefore, cannot be put in the class of 

 bacteria with spores, and they are very near to nonspore-bearing 

 organisms, or the vegetative cells of spore-bearings organisms, as 

 regards the effect of desiccation. They should be classed with the 

 more resistant of the nonspore-bearers. 



TABI,E 11. 



OF DESICCATION UPON BACTERIA 



