The file "Epidermal_nerve_density_data" has one row for each combination of a subject 
(child), body location, blister, and image.  The left-most column identifies the child, 
the second column identifies the location on the child (leg [calf] vs. thigh), the third 
column identifies the blister within child/location.  Replicate measures for a given 
subject/location/blisterNo are the different images taken of the blister.  The right-most 
column is epidermal nerve density, in units axons per mm^2.