84 TWELFTH REPORT. 



air was drawn through the filter plugs for at least five luiuiites to test 

 them and at the same time test the rubber connections. No seeds or 

 disinfectant were placed in U. Water was then drawn from ttask A 

 into flask D, shaken np, and again drawn oft'. This was done several 

 times, just as when there were seeds in flask ]). Flask D was then 

 taken out and set aside to incubate, as in the experimental cases. The 

 idea was to test the apparatus by using it as nearly as possible in the 

 same way as when seeds and disinfectants were present. As a matter 

 of fact, I took less pains in the control experiments to see that the 

 joints were perfectly tight tlian I did when I tested seeds. The fact 

 that flask I) was not opened during these control experiments cannot 

 be held as an objection, since any chance contamination, wheii tlie seeds 

 were placed in tlask D, is reached by shaking up the disinfectant so as 

 to thoroughly reach every part that might have become contaminated. 

 If the chance spores Avere able to survive that, thou it is manifestly im- 

 possible to kill those on the seeds, and the point is proven either way. 

 The onl}' place the disinfectant, when the seeds ar* treated, does not 

 reach is the inside of the small glass tube connecting B and D. It was 

 sterile when D was opened to admit the seeds and disinfectant and dur- 

 ing the brief jx'riod of time that D remained open the mouth of the 

 tube was directed downward, so no spores could drop in and 

 none could be drawn in, since there was no draft into it. 

 Besides, if any contamination could come from this source, in the case 

 of the seeds, it would have a^ipeared in the control as well. Yet none of 

 the controls showed any contamination. The conclusion seems irre- 

 sistible that the contamination must have come from the seeds. It was 

 thought that twenty controls were an ample number. 



The foregoing work lias convinced me that the results of formerly 

 published work are open to criticism in at least two res})ects: No ade- 

 quate proof is given that the seeds are really free from contaminating 

 organisms and no means are employed to so thoroughly remove the dis- 

 infectant that it could no longer act as a antiseptic. In view of the 

 foregoing results, we are forced to conclude that the majority ot cases of 

 so-called disinfection were merely cases of antisepsis. 



To antisepsis, and not to disinfection, we must probably look for 

 practical results. It makes no difference in physiological experimenta- 

 tion whether a few dormant organisms cling to the seedling or not. 

 what does the harm is their active gTowth and multiplication. Absolute 

 disinfection, which seems out of the question at present, is not essential. 



E. Lansing, April, 1910. 



