1. We receive good by doing good.
We | receive | good
=====|====================
| \by
\——-,doing | good
———————
+Explanation+.—The line representing the participle here is broken; the first part represents the participle as a noun, and the other as a verb.
+Oral Analysis+.—The phrase by doing good is a modifier of the predicate; by introduces the phrase; the principal word is doing, which is completed by the noun good.
+Passing+.—Doing is a participle; like a noun, it follows the preposition by, and, like a verb, it takes an object complement.
2. Portions of the brain may be cut off without producing any pain. 3. The Coliseum was once capable of seating ninety thousand persons. 4. Success generally depends on acting prudently, steadily, and vigorously. 5. You cannot fully sympathize with suffering without having suffered. (Suffering is here a noun.)
The +participle+ may be the +principal word+ in a phrase used as a +subject+ or as an +object complement+.
6. Your writing that letter so neatly secured the position.
—-, writing | letter
'————————————
\Your | \neatly \that
| \so
|
/ \ | secured | position
=========|========='===========
| \the
+Explanation+.—The diagram of the subject phrase is drawn above the subject line. All that rests on the subject line is regarded as the subject.