Commentary for Bava Batra 5:5
הַמּוֹכֵר רֹאשׁ בְּהֵמָה גַסָּה, לֹא מָכַר אֶת הָרַגְלָיִם. מָכַר אֶת הָרַגְלַיִם, לֹא מָכַר אֶת הָרֹאשׁ. מָכַר אֶת הַקָּנֶה, לֹא מָכַר אֶת הַכָּבֵד. מָכַר אֶת הַכָּבֵד, לֹא מָכַר אֶת הַקָּנֶה. אֲבָל בְּדַקָּה, מָכַר אֶת הָרֹאשׁ, מָכַר אֶת הָרַגְלָיִם. מָכַר אֶת הָרַגְלַיִם, לֹא מָכַר אֶת הָרֹאשׁ. מָכַר אֶת הַקָּנֶה, מָכַר אֶת הַכָּבֵד. מָכַר אֶת הַכָּבֵד, לֹא מָכַר אֶת הַקָּנֶה:
One who sells the head of a large beast has not sold the feet. [In the Tosefta it is stated: Where is this so? Where they are not accustomed to do so. But where they are, "all is according to the custom of the land."] If he sold the feet, he has not sold the head. If he sold the windpipe [i.e., the lung, so called because of its windpipe], he has not sold the liver. If he sold the liver, he has not sold the lung. But in a small animal, if he sold the head, he has sold the legs; if he sold the legs, he has not sold the head. If he sold the windpipe, he has sold the liver; if he sold the liver, he has not sold the windpipe.
Bartenura on Mishnah Bava Batra
English Explanation of Mishnah Bava Batra
But in the case of a small animal: If he sold the head he has sold the feet. If he sold the feet he has not sold the head. If he sold the lungs he has sold the liver. If he sold the liver he has not sold the lungs.
Mishnah five deals with what is included in the sale of large and small animals.
This mishnah draws a distinction between large animals, such as cows, and small animals such as sheep or goats. In section one we learn that each part of a large animal is significant enough to be sold separately. In other words, if one sells one part of a large animal, he has not necessarily sold another part of the animal with it. However, with small animals some parts are sold with others and some parts are sold alone. For instance, if one bought the head, the feet are automatically included. Likewise if one bought the lungs, the liver is automatically included. However, the opposites are not true. If one bought the feet he has not automatically bought the head. If one bought the liver he has not automatically bought the lungs.