Work in progress, produced by python code and http://www.cytoscape.org/ :

![eggs to compost](https://user-images.githubusercontent.com/117439/40447738-303ec846-5e99-11e8-953f-2be02a9a0272.png)

Eventually this could go in [Ignoring Externalities](https://forum.azimuthproject.org/discussion/2105/lecture-28-chapter-2-ignoring-externalities) but the discussion there was so focused I thought it would be disruptive right now. (And I am ignoring egg yolk and egg white for now, too.)