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 Pint The pint (, ; symbol pt, sometimes abbreviated as "p") is a unit of volume or capacity in both the imperial and United States customary measurement systems. In both of those systems it is traditionally one-eighth of a gallon. The British imperial pint is about 20% larger than the American pint because the two systems are defined differently. Almost all other countries have standardized on the metric system, so the size of what may be called a pint varies depending on local custom. The imperial pint (≈ 568 ml) is used in the United Kingdom and Ireland and to