846 Journal of Agricultural Research voi.xx.No. h 



and accordingly, that X-rays act on trichinae in the second of the three 

 ways mentioned above, is indicated by the results of the experiments 

 recorded here. 



METHODS OF EXPERIMENT 



The trichinous meat used in these tests was obtained from hogs (series 

 I, II, III, and V) and guinea pigs (series IV). The animals were arti- 

 ficially infected by feeding them trichinous pork. The infested pork to be 

 exposed to X-rays was obtained from hogs that were killed several months 

 after artificial infection. Trichinous guinea-pig meat was obtained from 

 animals kept about a month after artificial infection. 



Trichinous pork was packed in wooden or cardboard boxes in Wash- 

 ington, forwarded to Florida, where the exposure to X-rays was made, 

 and promptly returned to Washington, where it was fed to experimental 

 animals in order to determine the effects of the exposure. In a few 

 cases portions of the meat that had been exposed to X-rays were digested 

 in an acidified solution of scale pepsin, the decapsuled larvae were ex- 

 amined, and the results were compared with those of the feeding experi- 

 ments. Infested guinea pigs were shipped alive to Florida about 30 

 days after artificial infection. The animals were killed with chloroform 

 in Florida, the skins and viscera were removed, and the carcasses were 

 placed in boxes, exposed to X-rays, and returned to Washington. 



The feeding experiments were performed in Washington. A quantity 

 of the treated meat was ground up in a meat chopper and fed to a number 

 of rats and, in some cases, mice. Unless they died as a result of infection 

 with trichinae the animals were killed at various intervals and examined 

 for evidence of infestation with trichinae as noted in connection with 

 each experiment. Controls on the meat from the same lots as those 

 exposed to X-rays showed that in all cases in which it was possible to 

 maintain controls the untreated meat contained viable trichinae capable 

 of normal development. In those cases in which the entire carcasses 

 of trichinous guinea pigs were exposed to X-ray treatment it was of 

 course not possible to maintain controls. 



EXPERIMENTS 



SERIES I 



X-ray dosage. — The units of dosage used in this series of experiments 

 are described by the roentgenologist under date of January 20, 1917, 

 on which day the exposures to X-rays were probably made, 1 as follows: 



I adopted a purely arbitrary unit, 1,000 of which units are equivalent to a dosage 

 received at a distance of 5 inches from the focal spot of a Coolidge tube with a current 

 of 4.2 milliamperes and a pressure of 70 kilcvolts across the tube terminals. Treat- 

 ment continued for 42 minutes. In ordinary X-ray terms this is equivalent to 172 

 milliampere minutes with a 6% -inch gap and a 5-inch distance. 



1 The meat was received in Washington on January 22, and feeding experiments were begun on January 23. 



