TT #201 · Parshas Tazria · Aliyah 5 · Passuk 31
English: If the priest examines the netek and its appearance is not deeper than the skin, and there is no black hair in it, he shall isolate the netek for seven days.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:31
Torah Temimah cites Sifra (Toras Kohanim) for the rule for adjacent netakim separated by a path of hair.
Sifra — Vayikra 13, Midrash Sefer
English: The Sifra states the distinction this way: when the two adjacent netakim are separated by a path of hair, a case “from one place” is impure, whereas one “from two places” is pure.
Textual derivation
The Sifra distinguishes adjacent netakim by the “one place” versus “two places” classification when a strip of hair separates them. The distinction is preserved as stated in the source; the text here does not add a geometric explanation beyond that wording.