ते ह प्राणाः प्रजापतिं पितरमेत्योचुर्भगवन्को नः श्रेष्ठ इति तान्होवाच यस्मिन्व उत्क्रान्ते शरीरं पापिष्ठतरमिव दृश्येत स वः श्रेष्ठ इति ॥ ५.१.७ ॥
te ha prāṇāḥ prajāpatiṃ pitarametyocurbhagavanko naḥ śreṣṭha iti tānhovāca yasminva utkrānte śarīraṃ pāpiṣṭhataramiva dṛśyeta sa vaḥ śreṣṭha iti || 5.1.7 ||
7. The organs then went to their father Prajāpati and said, ‘Revered sir, who among us is the best?’ He replied, ‘He is the best among you on whose departure the body becomes totally untouchable’.
Te ha prāṇāḥ, those organs; pitaram prajāpatim etya, coming to their father Prajāpati; ucuḥ, said; bhagavan, revered sir; naḥ, among us; kaḥ śreṣṭhaḥ iti, who is the best; tān ha uvāca, he said to them; vaḥ, among you; yasmin utkrānte, on whose leaving; śarīram pāpiṣṭhataram iva dṛśyeta, the body appears to be untouchable; saḥ vaḥ śreṣṭhaḥ, he is the best among you.
We all know what happens when life leaves the body. It is not the same body. It shrinks. It becomes ugly. And soon it starts decomposing. No one wants to touch it. Prajāpati indirectly declared in this way that prāṇa was the best among them.
When Prajāpati said this, he changed his voice lest he hurt the other organs. The way he changed his voice is called kaku.