374 J. M. D. OLMSTED 
the wound healed rapidly, the edges of the cut closing together 
‘at the end of the second day, and from that time on only a fine 
white line in the skin showed where the incision had been made. 
Corresponding changes did not occur at precisely the same time. 
For example, many barbels fixed on the eleventh day after 
operation had taste buds in perfect condition, while in others 
all buds had disappeared. One could, however, readily make 
out the stages in the process. 
STRUCTURE OF NORMAL BARBELS AND THEIR TASTE BUDS 
To appreciate the results of the experiments in nerve cutting, 
an understanding of the histology of the normal barbels and 
taste bud is essential. The following description suppleménts 
the statements of Wright (’84) and Herrick (’01). The eight 
barbels of Amiurus are practically the same in form and structure. 
The two large barbels at the corners of the mouth are stiffened 
by very heavy cartilage, which will not cut well after the ordinary 
paraffin treatment. The other six barbels have only a small 
central core of cartilage which does not seriously interfere with 
sectioning, and for this reason the operations involved only these 
six barbels. The barbels are somewhat flattened laterally, the 
anterior edge being slightly broader than the posterior one (fig. 
16, 24). It is the epidermis of the anterior edge which bears the 
majority of the taste buds, for they lie closely crowded here and 
appear only at intervals on the other portions of the barbels. 
This concentration of the taste buds on the anterior edge is to 
be expected, since it is this portion of the barbel which touches. 
objects as the fish sweeps along the bottom in search of food. 
Unicellular glands, pigment cells, wandering leucocytes, and 
stratified epithelium compose the major portion of the epidermis. 
The central core of the barbel is occupied by a rod of cartilage, 
a large nerve trunk, blood-vessels, muscle, and a small amount 
of connective tissue. 
The taste buds are flush with the surface or even project 
beyond the level of the outer epidermal cells, especially toward 
the tip of the barbel, where the epidermis is relatively thin. 
They are never depressed, nor do they lie at- the bottom of a 
