Rashi explains that the difference between an injury to the cartilage and to ordinary skin is that cartilage does not repair itself and is therefore considered a permanent blemish. While the commentaries agree that the has’hus of our Mishnah refers to the cartilage, not all agree on the exact intention of the Mishnah. Some identify it with the tenukh mentioned in Sefer Shemot (29:20), which is defined as the middle protrusion in the ear, right next to the outer ear canal, explaining that animals have a similar structure inside of their ears. Many disagree, arguing that a blemish that is hidden in the body of the animal should not be considered a mum. According to their approach, the has’hus refers to all parts of the ear that are thicker than ordinary skin.
According to the Torah ( 15:19-22), while a healthy firstborn animal must be sacrificed, if the animal has a mum – a blemish – it is lame, blind, or has “any ill blemish whatsoever,” the animal cannot be sacrificed, but can be eaten in an ordinary manner.
What is included in the category of a mum? What is considered to be “any ill blemish whatsoever”? Many of the rules that establish the definitions of these categories are traditions, some of which are subject to disagreements among the Sages. The sixth perek (=chapter) of Masechet Bekhorot, which begins on today’s daf (=page) aims to respond to these questions.
The first example offered in the Mishnah of a “blemish” deals with a wound to the ear. The Mishnah teaches “if its ear has become defective, being cut or bored through from the has’hus – the cartilage – inward” it is considered a blemish, “but not if the defect is in the ear-lap.”
The term has’hus, or, as it is used in modern Hebrew sehus, appears in the Mishnah as referring to parts of the body that are not soft like flesh or skin, but appear to be a type of soft bone. In modern terminology, this is dense connective tissues of which we find three types: Fibrocartilage, Hyaline cartilage and elastic cartilage, which is present in the outer ear and is the case discussed in our Mishnah.