QUASILINEAR PREFERENCES: Please explain this!!

[X]

I am posting these pages from Varian's Intermediate Microeconomics :




I can't understand here these lines:
"As income increases the marginal utility of consumption of good 1 decreases.
When m = p2, the marginal utility from spending additional income on good
1 just equals the marginal utility from spending additional income on good 2.
After that point, the consumer spends all additional income on good 2."


I will be obliged if am explained.

[economist]

Consider increasing your income incrementally, starting from 0.
And note that marginal utility of good 1 decreases from infinity to zero as good 1 increases from 0 to infinity. But MU of good 2 is constant throughout. So, when you increase your income incrementally. You have 2 options . Spend that income on good 1 or on good 2, and you want to spend it on good which has higher MU.  So for small income. MU of good 1 is indefinitely large so you spent it all on good 1. But MU of good 1 decrease eventually and it becomes equal to 1 at some point and it then decreases below 1from then on. So when that point is reached, you dont consume anymore of good 1 but only good 2 as its MU is higher.
note that you cant argue that why he cant spend his incremental income on both goods in some proportion. As utility is separable. And there is nothing he cant achieve by consuming only one good, than by consuming both goods.