A quantitative study of forelimb innervation in relation to regenerative capacity in the larval, land stage, and adult forms ofTriturus viridescens
✍ Scribed by Peadon, Annie M. ;Singer, Marcus
- Publisher
- John Wiley and Sons
- Year
- 1965
- Tongue
- English
- Volume
- 159
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
The nerve fibers present at the amputation surface of the upper arm of the land stage and larval newt were counted and compared with values previously published by one of us on the adult. When expressed per unit area of surface, it was observed that the limb of the larva and the small land forms is more highly innervated than that of the adult. The values were 75.5, 47.6, and 27.7 fibers per (100 F ) 2 respectively for the larval, small land stage, and adult animals. The number of fibers per unit area of the larger land forms resembled that for the adult showing that the innervation ratio stabilizes at a time before the animal returns to water.
Calculations were also made of the number of motor and sensory fibers in the individual brachial nerves of the younger animals. Assuming the same quantitative threshold of nerve fibers is required to evoke regeneration of the limb in the young animal as is needed in the adult, it was possible to predict the effectiveness of each nerve and nerve component in supplying the neural requirement for regeneration. For example, we found that nerve 5, ineffective in itself to cause regeneration in adults, should evoke regrowth in younger forms, particularly in larvae. The predicted results correspond with experimental ones already published in the literature. The quantitative studies reported herewith are evaluated and discussed against the background of the important action of the nerve in regeneration of a body part. ~~ *Supported by grants from the American Cancer Society and National Institutes of Health. deviation +-2.9 rt 0.28 2 3.2 & 134.8 & 12.2 Standard