Abstract
Summary
1. No reactivation of the left diaphragm was seen by us in 15 dogs up to 20 months after complete section of the left phrenic nerve.
2. Microscopically all diaphragms showed complete muscular atrophy with degeneration or disappearance of nerve fibers, 14 to 20 months after complete section of the left phrenic nerve. It is difficult to conceive how such atrophic muscles could ever regenerate.
3. It is highly possible that phrenic exeresis in the neck of the human does not always result in complete phrenicotomy with subsequent atrophy of the diaphragm, but in a number of instances results in diaphragmatic palsy.
4. We found no evidence that the twelfth thoracic intercostal nerve or sympathetic innervation could influence the reactivation of the diaphragm in the dog.
5. Our experience with one diaphragm leads us to believe that a hemifunction of one half of a diaphragm may lead the fluoroscopist to assume that complete reactivation of that diaphragm has occurred.
6. The phrenic nerve above the point of section was able to convey reflexes 20 months after section; this was demonstrated by rise in blood pressure and increased respiration upon stimulation of the central end of the nerve, which were abolished when the nerve was cut central to the stimulating electrode.
7. No evidence of the gastro-cardiac symptom-complex of Roemheld was seen.
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