390 



CHAMBERLAIN AND VEDDER. 



would obtain in the practical sterilization of water by the apj^aratus above 

 described. The results are shown in the following 5 experiments. 



Experiment 3. — A number of ordinary hollow-ground slides were ster- 

 ilized and a large drop from the stock culture of amcebse was placed in 

 the hollow chamber of the slide. A culture was then made from this 

 drop by transferring a small loopful from the slide to a test tube con- 

 taining weak sterile bouillon. As soon as the culture was made, the 

 slide was placed under the center of the lamp and the current turned on 

 for a few seconds. After the exposure to the ultra-violet rays a second 

 culture was made in a similar manner from the drop on the slide. Table 

 III shows the results of such an experiment. 



Table III. — Experiment 3: Result of cultures from bouillon inoculated with 

 CDuoebcB. Cultures made before and after exposure to ultra-violet rays. ■ 



No. 



10 cm. from lamp. 



15 cm. from lamp. 



Culture 



before 



e.xposure. 



Exposure 



in 

 seconds. 



Culture 



after 

 exposure. 



Culture 



before 



exposure. 



Exposure 



in 

 seconds. 



1 

 Culture 1 



after 

 exposure. 



1 



+ 



5 



— 



+ 



5 



J- 



2 



+ 



5 



— 



+ 



5 



— 



3 



+ 



5 



— 



+ 



5 



+ 



4 



+ 



10 



— 



+ 



10 





5 



+ 



10 



— 



+ 



10 



— 



6 



~r 



10 



— 



+ 



10 



— 



7 



+ 



20 



— 



1' 



20 



— 



8 



+ 



20 



— 



+ 



20 



— 



9' 



H- 



20 



— 



+ 



20 



— 



10 



^^ 



30 



— 



+ 



30 



— 



11 



+ 



30 



— 



+ 



30 



— 



12 



+ 



30 



— 



+ 



30 



— 



It will be seen that in this experiment the amcebse were killed in 

 every trial at 10 centimeters from the lamp and were also killed in all 

 exposures of ten seconds or more at a distance of 15 centimeters. This 

 experiment was particularly satisfactory although it must be admitted 

 that all circumstances were very favorable, since the amcebse were in a 

 thin layer of clear fluid. 



Experiment J/..- — This was performed in a manner similar to experi- 

 ment 3. Distilled water was placed in ordinary staining dishes in 

 sufficient quantity to form a layer 2.5 centimeters deep. This water 

 was heavily inoculated with amoebs from the stock culture. A loopful 

 of this water was cultivated in a test tube of dilute bouillon in order 



