Confusion in Section 43 of Income-tax Act

I'm scratching my head over Section 43 of the Income-tax Act. It says that the profit from a sale of an asset is the consideration received, minus the cost of acquisition, plus or minus any other expenses. But then there's this sub-clause (b) which talks about "depreciation" and "capital gains". It seems Section 43 itself is trying to define capital gains, but it's not exactly clear. Isn't that what Section 45 is supposed to do? What am I missing? Anyone else as confused as I am?