What are the holes in Swiss cheese called?

Swiss cheese is a generic name in North America for several related varieties of cheese, mainly of North American manufacture, which resemble Emmental cheese, a yellow, medium-hard cheese that originated in the area around Emmental, in Switzerland. Some types of Swiss cheese have a distinctive appearance, as the blocks of the cheese are riddled with holes known as "eyes". Swiss cheese without eyes is known as "blind". (The term is applied to cheeses of this style made outside Switzerland, such as Jarlsberg cheese, which originates in Norway).

Baby Swiss and Lacy Swiss are two varieties of American Swiss cheeses. Both have small holes and a mild flavor. Baby Swiss is made from whole milk, and Lacy Swiss is made from low fat milk. Baby Swiss was developed in the mid-1960s outside of Charm, Ohio, by the Guggisberg Cheese Company, owned by Alfred Guggisberg.

In general, the larger the eyes in a Swiss cheese, the more pronounced its flavor because a longer fermentation period gives the bacteria more time to act. This poses a problem, however, because cheese with large eyes does not slice well and comes apart in mechanical slicers. As a result, industry regulators have limited the eye size by which Swiss cheese receives the Grade A stamp.