Menachot 74: The Altar Vs. The Kohanim; The System of Shittin

Today's Mishna teaches us about instances when the kohanim are permitted to eat all of the meal-offering and cases went the altar consumes all of the meal-offerings.  The one that consumes all of the meal-offering is considered to be "stronger".  

When the altar receives the entire offering:

• minchat kohen: the meal offering brought by a priest, could be voluntary or obligatory
• minchat kohen mashi'ach: the daily meal offering brought by the high priest in the morning and the afternoon
• minchat nesachim: the meal offering accompanying libations

According to the Gemara, other sacrifices might stay on the altar with no portion going to the kohanim.  However, each example notes that the altar does not receive everything in these cases.  For example, the kohanim receive the skin of the animal when it is given as an ola, burnt offering.  When libations are poured on the altar and the kohanim receive not, we learn that the wine is poured into the shittin, pipes and hollow spaces within and beneath the altar, and not actually poured onto the altar.

Steinsaltz teaches us about the plumbing system beneath the altar.  Two small holes on the south-west corner of the altar carried blood and wine libations to the water tunnel under the Temple Mount and on to Kidron valley.  The Ge'onim report that the shittin were one cubit wide by 600 cubits deep.  In Masechet Sukka (49a) we learned that young priests would be sent to remove the solidified remnants of wine once every 70 years.  They could not fully descend into the bottom of the pipe.  Instead they would go as far down as possible and use special tools to clean the walls of the huge area beneath the Temple.