16 A. J. D. DE LORENZO 



outside the taste bud. However, the slope of the curve from A to B 

 represents a gradual shift of labeled cells from the margins into the taste 

 buds. At about 100 to 200 hr a large number of labeled cells are seen 

 within the taste buds of the foliate papillae of the rabbit. Calculating 

 crude rates of turnover, we submit that the labeled cells migrate into the 

 taste buds about one cell every 30 hr. Beidler's data in the fungiform 

 papillae of the rat show a rate of migration of about one cell every 10 hr 

 (personal communication). The rates may well vary in the anterior tongue 

 as contrasted with the more protected posterior taste buds of the papilla 

 foliata. 



Since our results are preliminary and our experience with radioauto- 

 graphy is limited, the rates calculated may be somewhat in error. However, 

 on the basis of Beidler's work and our own prelimary results, we submit 

 that the life history of the gustatory cell is quite short and that synaptic 

 junctions are in a constant state of flux. This immediately poses many 

 interesting problems for the neurophysiologist and neuroanatomist. Only 

 the combined techniques of biophysics, chemistry and electron microscopy 

 will eventually correlate structure and function in this most interesting group 

 of chemoreceptors. 



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