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 measure in Canada, they are still 20% larger than the American ones. In the British and Irish metrication processes, the pint was replaced by metric units as the legally defined primary unit of measure for trading by volume or capacity, except for the sale of draught beer and cider, and milk in returnable containers. The pint can still be used in those countries as a supplementary unit in all circumstances. Legislation in the UK mandates the use of the pint as a measure for draught beer and cider (in pubs for instance). For milk, if returnable containers are used, the