{HEAD ~ Male Hartley guinea pigs} from Charles River, weighing 250 275 grams on arrival and {TAIL ~ 300 600 grams} at testing, serve as subjects in the experiment 
{ HEAD ~ Male Hartley guinea pigs } from Charles River , weighing 250 275 grams on arrival and { TAIL ~ 300 600 grams } at testing , serve as subjects in the experiment
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