Here's a photo. Doesnt look like a mouthpiece.

It's an electrical insulator, called a "wall tube". Early electrical wires often had no insulation, and later a paper insulation that was somewhat suspect. These were used to pass wires through objects (walls or ceiling joists and rafters) and protect them from shorting. Insulators came in a myriad of shapes for specific applications, "bobbin" styles that stood the wire away from objects were also common.

Yeah, you're right. I've seen those too.

Right on! Thanks so much, I was thinking hair curler? Whats a date on this insulator then, 1890-1920ish?

Update- Pretty easy to research- googled knob and tube wiring, aka K&T wiring. Plenty of pics, etc. Apparently used up until the 1950s in some areas. Copper wire was sometimes coated with asphalt soaked fabric or paper or rubber insulation, sometimes it was left bare. Still like to find the makers mark somewhere. This example looks like an early type with the hand applied lip.  Tube pics found online feature what appears to be a machined, angular lip rather than the organic lip we've got on my example, this could indicate that our's is an early example of a tube of this sort. Again, thanks StarRider and Doppler Dave.

Kool! This is why I love this site! Well done!

As others have stated, it's the tube, as in "knob-and-tube".  It's an insulator for when the wire runs pass through studs in the walls.  The positive and neutral wires typically run parallel to each other, offset by about 18" but shared neutral wires between multiple circuits was very common.  Cables were typically 12 AWG; however, they were typically only rated to 15 amps due the type of insulation they used (modern 12 AWG is rated at 20 amps).  In the absence of those insulators, you'd often see a fabric equivalent that is referred to as "loom" or "loomex", especially when entering junction boxes (it protects the cable from sharp edges).

I've never seen bare wire before in old homes but it's my understanding that k&t was the standard from the beginning through the 1930's.  Some older electricians continued wiring houses through the late 1940's using K&T.  When electricity was new technology, people were very concerned about fire risks, that (and the lack of adequate insulation materials) lead to the redundant safety aspects of K&T. 

It was replaced by metal clad (BX) cable (I think it stands for Bronx), which is basically flexible steel conduit that contained both the positive and neutral wires.  From my understanding, this evolution in cabling was also due to concern regarding fire safety and several cities, especially those which had a history of large fires, still require metal clad cable (it's modern equivalent is MC).  This is definitely the case in Chicago; all wiring has to be MC or in conduit.

It wasn't until the 50's and 60's that non-metallic (NM) wiring became the norm, which was essentially cloth wrapped positive & neutrals in a single cable.  By the 1970's, a single (typically uninsulated) ground wire was added to the cable.

Sorry for rambling but I have a 100 year old home that we've been slowly renovating for the past decade and electrical has been both a hobby and a constant headache for me...