Sentence:  The brain, we are to understand, is sufficiently complex to supoprt higher functions because it is composed of some 10,000,000,000 neurons; and, as if this were not sufficient to leave one <WSD>gape-mouthed</WSD> with uncritical awe, it is pointed out that each of these components connects with numerous other components, so that the possible number of sub-units or combinations exceeds the number of atoms in the universe. 
Meaning of the word marked with <WSD> tags:  Overwhelmed with awe or astonishment.