The human soul, in the moment of discontent with what happens, is likened to an ἀπόστημα (an abscess) and a φῦμα (a tumour, an unnatural growth) on the body of the cosmos. The medical terminology is not chosen by chance:

• ἀπόστημα — from ἀφίστημι ("to stand apart," "to separate"); in Greek medicine, an abscess — a pathological collection in the tissue, set off from the healthy. Galen defines ἀπόστημα as "τὸ συνεστὸς ἐν τόπῳ τινὶ τοῦ σώματος ὑγρόν" — "fluid gathered in some place of the body."
• φῦμα — from φύω ("to grow, to spring up"); a tumour, an unnatural growth, cancer or abscess in the broad sense. Like ἀπόστημα, it is an anomalous formation that ought not to be in healthy tissue.
• ἀπόστασις (two lines further) — cognate with ἀπόστημα: "standing apart," "separation," "withdrawal." Galen uses ἀπόστασις as a synonym of ἀπόστημα in its pathological sense.

The threefold consonance ἀπό-στημα / φῦμα / ἀπό-στασις is not accidental: all three retain the root of division (ἀπό-στ-). The image is built as the unfolding of a single semantic knot: the soul that stands apart from the cosmos is thereby an outgrowth rejected by its healthy structure.

Med. 2.16 — the main text of the image: ψυχὴ ... γίνεται ἀπόστημα καὶ οἷον φῦμα τοῦ κόσμου. The mechanism of the image is immediately spelled out: τὸ δυσχεραίνειν τινὶ τῶν γινομένων ἀπόστασίς ἐστι τῆς φύσεως — "to be vexed at any of the things that happen is a withdrawal from the nature [of the whole]." That is: discontent = separation = pathological growth. The logic is three-step: murmuring against nature → rupture of the bond with the whole → pneumatic detachment — and the soul becomes "not its own" with respect to the cosmos.

The image recurs in close forms:

• Med. 4.29 — "a piece split off" (ἀπόσχισμα) from the cosmos; no longer an abscess, but a separated chunk
• Med. 8.34 — the image of the severed hand or foot: "as a part separated from the body lies dead, so too the person who has stepped away from nature"
• Med. 9.23 — singling oneself out from the common τάξις (order) is a violation of the integrity of the whole

The image performs precisely the opposite work of the ordinary consolatory "don't be vexed, or you'll have it worse." Marcus shows: murmuring does not make me "worse off" — it makes me ontologically not myself. A healthy soul is a built-in part of the cosmos; a murmuring soul falls out of it, becoming a pathological formation. Not "you will suffer," but "you cease to be yourself" — this is a structural argument that bypasses ordinary consolatory squabbling.

Paired with aimless-wandering (02-07): there the soul was depicted in motion — aimless drift and circling; here, in a state, as a pneumatic tumour. Both images diagnose a disordering of the soul's link with the whole, but from different angles: one kinematic, the other pathological.

The inverse — 03-08: the portrait of the healthy soul is given through the negation of the same medical images: in the purified mind there is nothing πυῶδες (purulent), μεμολυσμένον (defiled), ὕπουλον (festering beneath the skin), and it is οὐδὲ ἀπεσχισμένον — "not split off" (the same ἀπο-σχ- root as the ἀπόσχισμα of Med. 4.29), yet also not προσδεδεμένον (not over-attached). Health is embeddedness-without-clinging: neither abscess nor severance.

Connection with the doctrines: this picture only makes sense within the DOGMAontology of the single cosmos (where part and whole are real as a pneumatic continuum) and within the DOGMAcosmopolis (the rational soul as a co-citizen). Without both background theses, "an abscess on the cosmos" would be an empty metaphor, not a diagnosis.