model = Sketchup.active_model   # Access the model
ents = model.entities           # Access the entities in the model
sel = model.selection           # Access selection object

vertex_array = []
edges2 = []

for _Count1 in 1..7 
   
   vertex_array.clear   # Clears the vertex_array to repopulate it with the newly added edge's vertices
   vertex_array = sel[_Count1 - 1].vertices
   edges2.clear   # Clears the edges2 array to repopulate it with the newly added edge's vertices
    
    # Since the connector/short (spine) edges connecting the long (rib) edges are always descending, ...
    # ... find the vertex with the lowest value for the z-coordinate to identify the next set of edges, ...
    # ... where to find the next short (vertebrae) edge.
    if vertex_array[0].position.z.to_mm > vertex_array[1].position.z.to_mm
      edges2 = vertex_array[1].edges # Gathers the edges connected to the second vertex (index 1) to the array of edges
    else
      edges2 = vertex_array[0].edges # Gathers the edges connected to the first vertex (index 0) to the array of edges
    end
    
   # Now we get rid of the short edge that was last added to the selection, since it was included ...
   # ... in the edges2 array, as it is also connected to the vertex used to gather the edges.
   # after removingt this edge there would only be 3 edges in the edges2 array.
   _LastSelId = sel[_Count1 - 1].object_id.to_s
   for myCount in 0..(edges2.length - 1)
      if edges2[myCount].object_id.to_s == _LastSelId
         edges2.delete_at(myCount)
      end
   end

   # After getting rid of the short edge that was last added to the selection, of the 3 edges left, ...
   # the shortest one (a vertebrae) should be the one to be the next edge to add to the selection.
   _MinLengthEdge = [edges2[0].length, edges2[1].length, edges2[2].length].min
   for myCount2 in 0..(edges2.length - 1)
      if edges2[myCount2].length == _MinLengthEdge
         _MinLengthEdge = myCount2
      end
   end

   # Now we just add the edge previously identified as the shortest in the edges2 array to the selection 
   sel.add edges2[_MinLengthEdge]   
 
end