Bhashya
एवं मांसान्यस्य पुरुषस्य, वनस्पतेः तानि शकराणिशकलानीत्यर्थः ।किनाटम्, वृक्षस्य किनाटं नाम शकले-भ्योऽभ्यन्तरं वल्कलरूपं काष्ठसंलग्नम्, तत् स्नाव पुरुषस्य ;तत्स्थिरम्- तच्च किनाटं स्नाववत् दृढं हि तत् ; अस्थीनिपुरुषस्य, स्नाव्नोऽन्तरतः अस्थीनि भवन्ति ; तथा किनाट-स्याभ्यन्तरतो दारूणि काष्ठानि ; मज्जा, मज्जैव वनस्पतेःपुरुषस्य च मज्जोपमा कृता, मज्जाया उपमा मज्जोपमा,नान्यो विशेषोऽस्तीत्यर्थः ; यथा वनस्पतेर्मज्जा तथा पुरुषस्य, यथा पुरुषस्य तथा वनस्पतेः ॥
In plain words
So: 'his flesh' means this person's own flesh, and for a tree the very same thing is called 'chips' — plain fragments. 'Kinata' is the name for what sits just inside those chips in a tree, a bark-like layer stuck to the wood — and in a person, that's the sinew. Call it 'firm' because, like a sinew, it really is tough. Bones sit just inside the sinew; timber sits just inside that same layer in the tree. And marrow — here there's nothing left to translate. The verse calls it 'the likeness of marrow' simply because it is marrow, no difference at all. Whatever the tree's marrow is, so is the person's, and whatever the person's is, so is the tree's.
Close to the Sanskrit
Thus, 'his flesh' [refers to] this person's flesh; for the tree, those same things are 'śakarāṇi' — meaning 'fragments'. 'Kināṭa': for a tree, kināṭa is the name for what lies further inside than the chips, in the form of bark, attached to the wood; that, for a person, is the sinew. '[The] firm one' — that kināṭa is firm indeed, like a sinew. '[The] bones' belong to the person; from inside the sinew, bones occur; likewise, from inside the kināṭa, there are pieces of wood, [that is,] timber. 'Marrow' — for the tree, marrow itself, and for the person too, has been described by 'the likeness of marrow'; a likeness of marrow is 'majjopamā' — meaning there is no further distinction; as is the tree's marrow, so is the person's, and as is the person's, so is the tree's.