The percussion tube has a similarly shaped body to the wireless electric tube, but the internal construction differs; it is fitted with a striker, below which is a percussion cap on a hollow brass anvil, and the tube is filled with powder.
With quick firing guns (those using metallic cartridge cases) the case itself is fitted with the igniting medium; in England these are called primers. For small guns the case contains a percussion primer, usually a copper cap filled with a chlorate mixture and resting against an anvil. The striker of the gun strikes the cap and fires the mixture. For larger guns an electric primer is used, the internal construction and action of which are precisely similar to the wireless tube already described; the exterior is screwed for the case. For percussion firing an ordinary percussion tube is placed in an adapter screwed into the case. In some foreign services a combined electric and percussion primer is used.
The first written reference to the breed was in 1814 ("Instructions to Young Sportsmen" by Colonel Peter Hawker), the first painting in 1823 ("Cora. A Labrador Bitch" by Edwin Landseer), and the first photograph in 1856 (the Earl of Home's dog "Nell", described both as a Labrador and a St. Johns dog). By 1870 the name Labrador Retriever became common in England. The first yellow Labrador on record was born in 1899 (Ben of Hyde, kennels of Major C.J. Radclyffe), and the breed was recognised by The Kennel Club in 1903. The first American Kennel Club (AKC) registration was in 1917. The chocolate Labrador emerged in the 1930s, although liver spotted pups were documented being born at the Buccleuch kennels in 1892. The first dog to appear on the cover of Life Magazine was a black Labrador Retriever called Blind of Arden in the December, 12th, 1938 issue. The St. John's dog survived until the early 1980s, the last two individuals being photographed in old age around 1981.
Labradors are medium-large, with males typically weighing 6580 lb (2936 kg) and females 5570 lb (2532 kg). The majority of the characteristics of this breed, with the exception of colour, are the result of breeding to produce a working retriever.
As with some other breeds, the Conformation (typically "Show", "English" or "bench") and the Field (typically "Working" or "American") lines differ, although both lines are bred in both countries. In general, however, Conformation Labradors tend to be bred as medium-sized dogs, shorter and stockier with fuller faces and a slightly calmer nature than their Field counterparts, which are often bred as taller, lighter-framed dogs, with slightly less broad faces and a slightly longer nose. However, Field Labradors should still be proportional and fit within American Kennel Club standards. With Field Labradors, excessively long noses, thin heads, long legs, and lanky frames are not considered standard. These two types are informal and not codified or standardised; no distinction is made by the AKC or other kennel clubs, but the two types come from different breeding lines. Australian stock also exists; though not seen in the West, they are common in Asia. These dogs are also very good with children.
The breed tends to shed hair twice annually or regularly throughout the year in temperate climates. Some Labradors shed considerably; however, individual Labradors vary. Labrador hair is usually short and straight, and the tail is quite broad and strong. The webbed toes of the Labrador Retriever make them excellent swimmers. The webbing between their toes can also serve as a "snowshoe" in colder climates and keep snow from balling up between their toesa condition that can be painful to other breeds with hair between the toes. Their interwoven coat is also relatively waterproof, providing more assistance for swimming.