Chapter Two Gage’s Brain Revealed talks about the problem that neurologists noticed with Gages’ accidence and investigate the solution by introducing the big picture of the brain. 
Professors Broca and Wernicke proposed that the lesions in the left frontal lobe could cause language impairment. However, the damage to Gage’s left frontal lobe did not had him to get any language impairment. Harlow, the person who was working on Gage, did not get the chance to study Gage in depth until several years after Gage’s death. He got Gage’s skull and found out the part of the brain that had been damaged by the iron, but the conjecture could be erroneous because of individual brain variation. 
After that Damasio introduces the anatomy both the human nervous system. He mentions the microscopic single neurons (nerve cells) and the macroscopic systems. He shows the main component of the central nervous system in three dimensions. Then he sections the central nervous system to present the difference between dark and pale sectors (gray matter and white matter). A map of the main brain areas identified by Brodmann depicts cerebral cortex, which is the the outer layer of the cerebrum. Damasio explains the main components of neurons including cell body, dendrites and portion of axon. Moreover, he talks brings out his disagreement about the probability of revealing the connectivity of neuroanatomy because “each neuron talks to a few others but never to most or all of the others”. 
Gage’s skull was later photographed for helping  narrow down the range of possible courses for the iron bar. Hanna Damasio and her colleagues concluded the functions of prefrontal cortices including planning for the future, controlling attention, deciding action and so on. 
I think Gage’ case is a good support for the identity theory, which claims that mind and  body are one thing because changes in Gage’s brain structure obviously changes Gage’s characters.