Romans 12:4,5

“ For as we have many members in one body, and all members have not the same office; so we, who are many, are one body in Christ, and severally members one of another. ”

The organization of the human body should be an example to the believer to make him perceive the necessity of limiting himself to the function assigned him. Not only, indeed, is there a plurality of members in one body, but these members also possess special functions, varied capacities (Romans 12:4). So in the church, which is the organ of Christ's life on the earth (His body), there is not only a multiplicity of members, but also a diversity of functions, every believer having a particular gift whereby he ought to become the auxiliary of all the rest, their member. Hence it follows that every one should remain in his function, on the one hand that he may be able to render to the rest the help which he owes them, on the other that he may not disturb these in the exercise of their gift. See the same figure more completely developed, 1 Corinthians 12

The form καθ᾿ εἷς, instead of καθ᾿ ἕνα, occurs only in the later Greek writers.

Instead of ὁ δέ (in the Byzs.), which is the pronoun in the nominative, the Alexs. and Greco-Latins read τὸ δέ, which may be taken as an adverbial phrase: relatively to, or better, as a pronoun, in the sense: “ and that, as members of one another.