Figure 13.

(Top) Colored balls mark certain geometric criteria that potentially define a bouton. In this example, the blue spheres indicate the position along the centerline where the maximum radius of the cross-sectional surface area was greater than 0.2 micrometers. Red spheres indicate where the cross sectional surface area of the axon is decreasing by a factor of 2 over a distance 0.2 micrometers (looking from right to left). Green spheres indicate where the cross sectional surface area of the axon is increasing by a factor of 2 over a distance 0.2 micrometers (looking from right to left). (Bottom) Two user-chosen balls are used to define and extract a new bouton object.