9. To separate quotations, or similar brief expressions from the preceding part of the sentence.
Cæsar reported to the Senate, “I came, I saw, I conquered.”
The question is, What shall we do next?
10. To indicate the omission of the verb in compound sentences having a common verb in several clauses.
One man glories in his strength, another in his wealth, another in his learning.
11. To separate phrases containing the case absolute from the rest of the sentence.
The form having been locked up, a proof was taken.
12. Between words or phrases in apposition to each other.
I refer to DeVinne, the great authority on Printing.