Positive disagreements in modern treatises on the subject are few.

The whole matter, however, turns so much on the use made of certain general principles and the field is so vast that different writers vary greatly in their statements and even in their ideas of what ought to be stated.

It is very difficult to strike the right mean between a set of rules too fragmentary and too incomplete for any real guidance and a set of rules too long to be remembered and used.
After all possible has been done to indicate the best usage it remains true that the writer or the printer must, in the last resort, depend very largely on himself for the proper application of certain principles.

The compositor may find himself helped, or restricted, by the established style of the office, or he may at times be held to strict following of copy.

When left to himself he must be guided by the following general principles: I.The comma is used to separate for the eye what is separate in thought.
The comma is not intended to break the matter up into lengths suited to the breath of one reading aloud.
The comma is not an aesthetic device to improve the appearance of the line.
II.