The Four Nutriments: what do the metaphors in SN 12.63 mean?

In the Puttamansa Sutta, the Four Nutriments ('ahara') of physical food, sense contact, intention & consciousness are discussed using four comparative similes ('metaphors'). The 1st simile of eating the flesh of one's own son (merely for the sake of crossing the desert) is very straightforward. However, the remaining three similes of a '*skinned cow*', of '*two strong men dragging a man into a pit of fire*' & of a '*thief punished by a king*' are not obvious in their meaning. These three similes are: > *And how, O monks, should the nutriment **sense-impression** be considered? Suppose, O monks, there is a skinned cow that stands close > to a wall, then the creatures living in the wall will nibble at the > cow; and if the skinned cow stands near a tree, then the creatures > living in the tree will nibble at it; if it stands in the water, the > creatures living in the water will nibble at it; if it stands in the > open air, the creatures living in the air will nibble at it. Wherever > that skinned cow stands, the creatures living there will nibble at > it.* > > *And how, O monks, should the nutriment **volitional thought** be considered? Suppose, O monks, there is a pit of glowing embers, filled > to cover a man's height, with embers glowing without flames and smoke. > Now a man comes that way, who loves life and does not wish to die, who > wishes for happiness and detests suffering. Then two strong men would > seize both his arms and drag him to the pit of glowing embers. Then, O > monks, far away from it would recoil that man's will, far away from it > his longing, far away his inclination. And why? Because the man knows: > 'If I fall into that pit of glowing embers, I shall meet death or > deadly pain.*' > > *And how, O monks, should the nutriment **consciousness** be considered? Suppose, O monks, people have seized a criminal, a robber, and brought > him before the king saying: 'This is a criminal, a robber, O Majesty! > Mete out to him the punishment you think fit!' Then the king would > tell them: 'Go, and in the morning strike this man with a hundred > spears!' And they strike him in the morning with a hundred spears. At > noon the king would ask his men: 'How is that man?' — 'He is still > alive, Your Majesty.' — 'Then go and strike him again at noontime with > a hundred spears!' So they did, and in the evening the king asks them > again: 'How is that man?' — 'He is still alive.' — 'Then go and in the > evening strike him again with a hundred spears!' And so they did.* What do we think each of these similes means?