Using an author's citations in a peer reviewed articles I'm reading this peer-review article which I'm certainly going to use as a source for my paper. The article is written by Robert E. Denton. 

Now, in this Denton article, Denton quotes an excerpt from another author, Murray Edelman. This excerpt is intriguing, and I would like to add it to my paper as an additional source. Denton provides text information of Edelman's work on his references page. 

My questions are these: do scholars ever do this? and by "this" I mean do research, and in there research(in the peer reviewed article he or she is reading) find an excerpt or quote of another work and include that excerpt or quote in their work without reading the entire article or book which that excerpt from? 

Is there a specific term for this type of citation? I have a feeling that there isn't.

Is it an unspoken practice? 

Now, I would be using a similar interpretation to Edelman's excerpt that Denton's uses because there are only so many interpretations of four lines of text, but i would be relating it to very a different social phenomenon(these are socio-political works), so I can't exactly say that this is plagiarism. 

Would it be okay to quote Denton's assertion, and then quote the Edelman excerpt which he uses to support his assertion, and thereore use both quotes successively to support my own argument?
It's a bad idea. Go find the original source. There are stories of misquoted data from citations being propagated through the literature because one early paper didn't go all the way back to the original source. 

If E quotes D correctly, you're free to draw on both their arguments with proper citation to both.