THE NERVE IN DEVELOPMENT OF TASTE BUDS 467 



A column of large hyaline cells extends from the old cartilage 

 nearly to the basement membrane of the epidermis at the very 

 tip of the new portion of the barbel. In the younger specimen 

 with a regenerated end, i.e., 2 to 3 mm. in length, these precartil- 

 age cells stain a light blue, but in later stages of regeneration 

 they take the typical brilliant red of the old cartilage. These 

 cells are readily distinguishable by their form and staining prop- 

 erties. Along the anterior border of this column of precartilage 

 is always seen, even in the shortest regenerated pieces, a small 

 amount of fibrous material which stains the characteristic lilac 

 hue, and which when traced to its origin is always found to be 

 continuous with the old nerve trunk. Certain sagittal sections 

 bring out this relationship most favorably in a single section, and 

 the connection can be readily traced in a series of transverse cross- 

 sections. These fibers extend in bundles between the rod of pre- 

 cartilage and the germinative layer of the epidermis throughout 

 practically the whole length of the regenerated tip of any barbel. 



When the regenerated end of a barbel is less than 2 or 3 mm. 

 in length, the germinative layer of the epidermis extends in a 

 smooth unbroken sheet around the entire new end. Both trans- 

 verse and sagittal sections show this unbroken line, and yet the 

 nerve extends practically throughout the length of the new piece. 

 But when a length of 3 to 4 mm. is reached, one can see several 

 indentations in the germinative layer. These appear first in the 

 region near the junction between the old and new tissue, and par- 

 ticularly along the anterior border of the new nerve. These 

 indentations are the beginnings of the dermal papillae, the invari- 

 able forerunners of the taste-buds. Each papilla is filled with a 

 small bundle of nerve fibers which stands out from the nerve 

 trunk like a small button, almost as if they had exerted such 

 force in their growth out from the nerve that they had indented 

 the germinative layer at that spot. 



Later stages of regeneration showed the presence of fully de- 

 veloped taste-buds along the whole length of the regenerated end, 

 mainly concentrated, however, along the edge nearest the nerve. 

 The development of mature taste-buds after the formation of the 

 dermal papillae is to be described in a later paper. 



