This unique chapter of 20 verses deals with the indwelling spirit and the Supreme Spirit, and the perishable man and the imperishable Purusha (Supreme Spirit). It can be seen that v9, v12, v13, v14, and v15 are clear digressions after the fascinating proposition in,
Ch15, V8
Wind as carries scent of flowers
While leaving them as is where,
In like fashion Spirit from frames
Moves its awareness to rebirths.
śharīraṁ yad avāpnoti yach chāpy utkrāmatīśhvaraḥ
gṛihītvaitāni sanyāti vāyur gandhān ivāśhayāt
Now, here follows this obvious interpolation.
V9
śhrotraṁ chakṣhuḥ sparśhanaṁ cha rasanaṁ ghrāṇam eva cha
adhiṣhṭhāya manaśh chāyaṁ viṣhayān upasevate
Using the sense perceptions of the ears, eyes, skin, tongue, and nose, which are grouped around the mind, the embodied soul savors the objects of the senses.
Hence, sans v9, in continuity to v8, the narrative runs thus,
Ch15, V10
Know not fools in lifetime theirs
Nature of Spirit thus lies in them
But ever on move from frame to frame.
utkrāmantaṁ sthitaṁ vāpi bhuñjānaṁ vā guṇānvitam
vimūḍhā nānupaśhyanti paśhyanti jñāna-chakṣhuṣhaḥ
Ch15, V11
This by striving wise realize
Fail though naive in spite of it.
yatanto yoginaśh chainaṁ paśhyanty ātmany avasthitam
yatanto 'py akṛitātmāno nainaṁ paśhyanty achetasaḥ
that is broken yet again by the digressions in V12 thru V15 thus:
V12
yad āditya-gataṁ tejo jagad bhāsayate 'khilam
yach chandramasi yach chāgnau tat tejo viddhi māmakam
Know that I am like the brilliance of the sun that illuminates the entire solar system. The radiance of the moon and the brightness of the fire also come from Me.
V13
gām āviśhya cha bhūtāni dhārayāmy aham ojasā
puṣhṇāmi chauṣhadhīḥ sarvāḥ somo bhūtvā rasātmakaḥ
Permeating the earth, I nourish all living beings with My energy. Becoming the moon, I nourish all plants with the juice of life.
V14
ahaṁ vaiśhvānaro bhūtvā prāṇināṁ deham āśhritaḥ
prāṇāpāna-samāyuktaḥ pachāmy annaṁ chatur-vidham
It is I who take the form of the fire of digestion in the stomachs of all living beings, and combine with the incoming and outgoing breaths, to digest and assimilate the four kinds of foods.
V15
sarvasya chāhaṁ hṛidi sanniviṣhṭo
mattaḥ smṛitir jñānam apohanaṁ cha
vedaiśh cha sarvair aham eva vedyo
vedānta-kṛid veda-vid eva chāham
I am seated in the hearts of all living beings, and from Me come memory, knowledge, as well as forgetfulness. I alone am to be known by all the Vedas, am the author of the Vedānt, and the knower of the meaning of the Vedas.
As can be seen, after the above digressive spell, v16 'n v17 put the discourse back on its logical course thus:
Ch15, V16
Perish all beings though in time
Perishes not the Spirit in them
dvāv imau puruṣhau loke kṣharaśh chākṣhara eva cha
kṣharaḥ sarvāṇi bhūtāni kūṭa-stho 'kṣhara uchyate
Ch15, V17
Self Mine Highest that sustains
Is but different from that One
uttamaḥ puruṣhas tv anyaḥ paramātmety udāhṛitaḥ
yo loka-trayam āviśhya bibharty avyaya īśhvaraḥ
Hence, the verses without chapter prefix are but interpolations