External gills usually contains muscle tissue, and may be moved by the animal as a free appendage, in order to stir up stagnant water. The stalk is lined by many thinly walled filaments (fimbriae), containing the majority of blood vessels used in gas exchange. Animals usually have one external gill originating on each gill arch (except the hyoid), which leads to there being three pairs of external gills in salamanders, and four in the gilled larvae of lungfish. External gills External gills are the gills of an animal, most typically an amphibian, that are exposed to the environment, rather than set inside
Pint glass present, the capacity line. There are no legally prescribed sizes for beer volumes, but the stated capacities, which are a legal requirement, must be formally tested by the hotelliers and breweries. In Canada, Federal law mandates a standard imperial pint. However, this law is rarely enforced, and establishments typically sell US pints or other measures as "pints." The Republic of Ireland uses the imperial 20 fl oz pint measure (≈568 ml), where legal metrology marks are used to show that a glass has passed inspection by the National Standards Authority of Ireland, a state-run body which enforces a number of