Mishnayos Negaim Perek 10 Mishnah 9

וניתק כל ראשו – that the bald, blanched spot spread throughout the head, whether that he was certified as a leper with golden hair, whether he was certified as a leper through spreading.

טהור – that in all of it, spreading all over purifies (see Tractate Negaim, Chapter 7, Mishnah 5 and Chapter 8, Mishnayot 1 and 2). And from where do we learn that spreading throughout purifies in the head, as it is written (Leviticus 13:40): "ואיש כי ימרט ראשו קרח הוא טהור הוא"/ “If a man loses the hair of his head and becomes bald, he is pure.” Regarding the beard, from where do we learn [that the same is the case]? The inference teaches us: "ואיש"/if a man – to include the beard. But if the bald, blanched spot comes throughout at the outset, he is not pure, that just as if it turns all white at the beginning, he is not pure with regard to the bright white spot on the skin.

אין מעכבין זה את זה – if there was a bald, blanched spot on his head like the size of a split [Cilician] bean and afterwards all of his head became torn loose, even though the beard was not torn loose, he is pure. And similarly, when there is white spreading all over in the beard, but it doesn’t spread all white in the head, he is pure, for they do not hinder one another.

ודין הוא – that they do hinder.

שיש דבר אחד מפסיק ביניהן – that the hair of the head and of the beard that they do not become defiled with the bright white spot on the skin that intervenes between the skin of the face to the rest of the body. But the skin of the face and the rest of the body do hinder each other, for all that is appropriate to be defiled through the plague of the bright white spot on the skin hinders the eruption of the bright white spot on the skin which causes the leper to be declared clean.

אין מצטרפין זה עם זה – in the place that the head and the beard join together. If a half of a split [Cilician] bean was to originate in this one (i.e., the head) and a half of a split [Cilician] bean was to originate in that one, they do not combine.

ואין פושין מזה לזה – if there is a bald, blanched spot the size of a split [Cilician] bean on the head near/adjacent to the beard, and at the end of the first week or at the end of the second week or after the release, it spread on the beard, it is not considered spreading.

מן הפרק של לחי – [from the joint of the] upper [jawbone]. He pulls/stretches a thread from ear to ear, all that is from the thread and above is the head, and all that is from the thread and below is the beard.

פיקה של גרגרת (thyroid cartilage/Adam’s apple) – the top of the thyroid cartilage begins to protrude and go downward, and the flesh that surrounds the thyroid cartridge from outside is called פיקה /protruding cartilage.