212 Journal of Agricultural Research voi. xvii, no. 5 



EXPERIMENTS WITH ENCYSTED LARV^ 



The experiments on decapsuled larvae were supplemented by experi- 

 ments on encysted larvae in their natural location in pieces of infested 

 muscle, the earlier of these .experiments being made by the senior writer, 

 the later, as noted, by the junior writer. 



Experiment ii (March 31, 191 3). — Small pieces of meat from a tri- 

 chinous rat were placed in a beaker of water (about 500 cc.) in a constant- 

 temperature oven. The temperature of the water increased from an 

 initial temperature of 18.4° to 48.4° C. in i hour and 10 minutes, at 

 which time a piece of the meat was removed. Ten minutes later, when 

 another piece was removed, the temperature had reached 51°. Eleven 

 minutes after this at a temperature of 52.8° another piece was removed. 

 After another period of 15 minutes, when the temperature had reached 

 55°, another piece was removed. Thirty-seven minutes later, when the 

 thermometer registered 59.8°, another piece of meat was removed. A 

 few larv^ae were isolated by dissection from these various pieces of meat 

 and examined under the microscope. The larvae from the pieces heated 

 to 48.4° and 51° were alive and active. One out of four larvae from the 

 piece heated to 52.8° showed slight movements; the others were inactive. 

 Those from the pieces heated to 55° and 59.8° were inactive when exam- 

 ined. The results of direct examination of the larvae were checked by 

 feeding the various pieces of meat to guinea pigs. The guinea pigs fed 

 with the meat which had been heated to 48.4° and 51° became heavily 

 infected; those fed the pieces heated to 52.8°, 55°, and 59.8^ remained 

 free from trichinas. 



Experiment 12 (April i, 191 3). — Several small pieces of rat muscle 

 were placed in a vessel containing 500 cc. of water and heated in an 

 oven from an initial temperature of 16° to a temperature that reached 

 55° C. at the end of two hours. Pieces of meat were removed at tem- 

 peratures of 51.2°, 52.2°, 53°, and 55°. A few larvae from each piece 

 of meat thus removed were isolated and examined directly on a warm 

 stage. Samples from these pieces of meat were also fed to guinea pigs, 

 which were killed about a month after feeding. The direct examination 

 of the larvae on a warm stage showed that, with the exception of those 

 from the meat heated to 55°, the majority were alive and responded to 

 thermal stimulation. Those heated to 55° were loosely coiled and did 

 not become active on the warm stage. 



The results of the feeding experiments were as follows : The guinea pig 

 that was fed meat heated to 51.2^0. was killed seven da3^s after feeding 

 because it became sick. The muscles were negative, but one pregnant 

 female trichina was found in the intestine. The guinea pig that was fed 

 meat heated to 52.2° was killed about five weeks after feeding, and only 

 one encysted larva was found in the diaphragm. No parasites were 

 found in the intercostal muscles. The guinea pig that was fed meat 



