ROLE OF HOST IN INITIATION OF DEVELOPMENT OF PARASITIC STAGE OF TRICHOSTRONGYLUS RETORTAEFORMIS (NEMATODA)

1. 1. Development of the parasitic stage was initiated in the stomach of rabbits when the infective juveniles exsheathed. 2. 2. Apparently, the host provided a stimulus for exsheathment and stimulated juveniles produced a substance which attacked the sheath. 3. 3. In vitro, the stimulus for exsheathment depended upon the concentration of undissociated carbonic acid, pH and temperature; the stimulus in vivo was probably similar. 4. 4. Stomach and duodenal contents were examined for factors that might stimulate development of the parasite. 5. 5. Stomach contents contained less sodium and potassium than duodenal contents, but the osmotic pressure of contents from both regions was about 300 mOsm. © 1968.