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REGENERATION IN VERTEBRATES: 



THE ROLE OF 



THE WOUND EPITHELIUM* 



Marcus Singer and Miriam M, Salpeter^ 



CORNELL UNIVERSITY 



A central problem in the regeneration of body parts in amphibians and 

 other vertebrates is the role that the old tissues of the stump play in the 

 formation of the new structure. In regeneration, unlike the situation in 

 embryonic development, the new part develops in close physical rela- 

 tion with the old. Indeed, the cells of the regenerate arise either directly 

 from stump tissues by morphological dedifferentiation, according to 

 the now-prevalent view, or from scattered embryonic reserve cells. Epi- 

 dermis gives rise to new epithelium by direct migration; nerve fibers re- 

 generate into the new growth; and blood, containing metabohc prod- 

 ucts and hormones of the adult body, supplies the developing part. 

 The individual tissues of the stump are important for the new growth, 

 but the precise nature of the role that each plays is as yet unknown. We 

 wish to dwell upon the influence of only one of these tissues, the epi- 

 dermis, on regeneration of a body part. Our thoughts are in part specu- 

 lative, but we have some experimental information which we believe 

 lends reason to these theories and makes their consequences worth 

 further evaluation. 



Much of our discussion concerns regeneration of the amphibian 

 limb, and so, before assessing the role of epidermis, it may be well to 

 review the sequence of regenerative development of that part in the 



* This work teas supported in part by grants from the American Cancer 

 Society and from the National Institutes of Neurological Diseases and Blindness of 

 the National Institutes of Health, U. S. Public Health Service. 



f Public Health Service Research Fellow of the National Cancer Institute. 



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