April, '13] 



MORGAN AND RUNNER: ROENTGEN RAYS 



227 



-at which rate the tubes could be used about thirty minutes contin- 

 uously. When the amperage is. increased the tubes heat up quickly 

 and must be changed. Changing and regulating the tubes consumes 

 so much time that more frequent changes than every half-hour can- 

 not be considered in commercial work. 



During our experiments the machine was tested at the commercial 

 adjustment, and afterward the most severe exposures were given of 

 which the machine was capable. Tubes were run both "hard" and 

 "soft," the time of exposure varied from a few seconds to one hour, 

 the voltage from 30,000 to about 75,000 and the amperage from 1| 

 milliamperes to 14 milliamperes, except in one experiment when the 

 amperage reached 20 milliamperes for 30 seconds. In most instances 

 instead of moving the material through the cabinet upon the carrier, 

 it was placed the closest possible to one of the targets or at the 

 common focus of the two targets. 



The following is a brief resume of the experiments in tabular form: 



TABLE SHOWING DETAILS OF X-RAY EXPERIMENTS UPON LASIODERMA SERRICORNE FABR., 



AT TAMPA, FLA. 



No. of experiment 



Parallel , Current 

 spark gap ' (milliam- 

 i peres) 



Stages exposed 



li-2i 



12-14 



11-1^ 



li 



3 



3 



3i 



~i 



2-2i 



2-21 



2i&2J 



2^-.1 



adults, eggs, larvae 

 adults, eggs, larvae 

 adults, eggs, larvae 

 eggs, larvae, pupje 

 eggs 



eggs 



eggs 



all stages 



all stages 



all stages 



all stages 



all stages 



adults, larva, eggs 



all stages 



* The exposure in No. 2 was, 5 min. at 8 miUiamperes, 1 min. at 9 milliamperes, 30 set^s. at 20 milliamperes and 

 3 min. at from Ij to 2^ milliamperes. 

 ** The total time in No. 2 w:is 9J minutes. 



General results of the above experiments: — the life history of the 

 treated material in every experiment proceeded normally as in the 

 check. Results were, therefore, negative. 



A detailed discussion of two of the experiments will serve to indicate 

 the results obtained in all. Experiment No. 3. The following mate- 

 rial was used: eggs deposited the night of October 6, 20 larvae and 



