In the present study, 264 young (42 + 2 days of age) Sprague-Dawley male albino rats (weighing 150-170 g; x = 159- 11) were used. The larvae used for infecting experimental rats were obtained by peptic-HC1 digestion from the skeletal muscles of stock rats that had been infected for not less than 60 days. Experimental rats were exposed to infection by intubation of 3000 - 100 larvae (suspended in 5% gelatin) deeply into the retropharynx by means of a blunt ball-tipped needle. Starting on day four and continuing through day 15 postinoculation, 22 rats per day were killed with ether fumes. The abdominal and thoracic cavities were quickly opened, and the lungs, liver, and kidneys were carefully excised. All