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 certain steps be taken to ensure that a pint of beer is indeed a pint. Though this can be achieved using "metered dispense" (calibrated pumps), the more common solution is to use certified one-pint glasses. Until recently these had a crown stamp indicating that the certification had been done by an agency of the Crown. The number etched upon the glasses stands for the manufacturing company or site. Most pint glasses used in the United Kingdom today have actually been produced in France. Under the EU Measuring Instruments Directive (Directive 2004/22/EC), the certification of measuring instruments and devices used in