Abstract
1. The responses of Various portions of the excised alimentary canal of Xenopus laevis (the South African clawed toad) to certain autonomic drugs have been noted.
2. (a) Pilocarpine produces contraction of the esophagus, stomach, duodenum and rectum, and relaxation is produced by the subsequent addition of atropine.
(b) In the ileum pilocarpine fails to show contraction. Relaxation is seen with strong concentrations, and atropine is able to produce a further relaxation.
3. Various theories have been considered in an attempt to account for this difference in response.
4. It is claimed that the entire alimentary canal of Xenopus is supplied by motor parasympathetic fibers. In the ileum the motor supply is poor and the muscle wall thin and ill developed, and pilocarpine by acting as a direct depressant of muscular tissue leads to relaxation.
5. The possible presence of inhibitory parasympathetic fibers in the intestine is receiving attention.
6. Physostigmine has no action on the parasympathetic system of Xenopus. In large doses it depresses muscular tissue.
7. Adrenaline produces relaxation of all portions of the alimentary canal of Xenopus, and barium causes contraction.
8. The responses of the alimentary canal of Xenopus laevis to autonomic drugs are very similar to those of the mammalian digestive tract.
9. The reactions described above appear to be independent of the sex and period of captivity of the animals, the season, mild fluctuations in temperature and variations in hydrogen-ion concentration.
Footnotes
- Received June 25, 1931.
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