<human-brain>
  <summary>A human neocortex contains four lobes.</summary>
  <neocortex>
    <lobes>
      <lobe id="frontal" />
      <lobe id="parietal" />
      <lobe id="occipital" />
      <lobe id="temporal" />
    </lobes>
  </neocortex>
</human-brain>
<dolphin-brain>
  <summary>A dolphin brain contains three hemispheres.</summary>
</dolphin-brain>