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136 would ignite 1 gases or other materials with which it might come in contact. Omitting technical detail, this form of bullet is organized to contain a charge of yellow phosphorus coated with copper phos- phide or aluminium dust in the head. The base is sealed, but a small hole is punched in the side of the bullet and closed with an easily fusible alloy containing a high percentage of bismuth. The heat generated by the passage of the bullet through the barrel of the gun causes this alloy to melt, at the same time causing the yellow phos- phorus to become molten. Upon exit from the barrel, the centrifugal force produced by the spinning of the bullet throws the molten phosphorus through the side hole and upon contact with the air the phosphorus burns leaving a trail of smoke and fire streaming from the bullet. Incendiary bullets burn over a range of approximately 300 yd. and are so loaded as to shoot similarly to service ammunition at that range. Incendiary cartridges are distinguished from other types of ammunition by special markings.

The use of various standard-calibre incendiary bullets against ob- servation balloons and dirigibles was supplemented by the develop- ment of a larger calibre ( 1 1 mm.) tracer incendiary cartridge for use at longer ranges. The bullets are generally turned out of solid brass rod and are approximately 1-34 in. long. The tracer incendiary composition produces a white or a red flame according to the chem- icals used. This composition is mixed and compressed into the brass bullets so as to withstand the pressure of the cartridge when fired. The flame from the propellant ignites the composition, which burns for at least 1,200 yards. The cartridge case is of the rim type and is loaded with a propellant to give a muzzle velocity of 2,000 to 2,350 ft. per second.

Combinations of the various types of bullets described above have been tried out experimentally with different degrees of success. The inspection of all of these types is very rigid, as all ammunition for aircraft use must be specially selected, in particular because hang- fires may be dangerous in aircraft machine guns synchronized with the propeller.

Many types of armour-piercing bullets were used during the World War in order to attack the light armour-plate of aeroplanes, tanks, etc. This class of bullet, with its steel core, required considerable experi- mental work and may still be considered as in the development stage. It consists principally of a cupro-nickel jacket, inside which is a hardened steel core incased in a lead envelope. The action may be briefly described as follows :

Upon striking the armour-plate, the jacket splits and a portion of the lead in the nose of the bullet is trapped between the hardened point of the steel core and the surface of the hardened armour-plate. This soft mass of lead produces a protective coating for the nose of the steel core and thus aids penetration. The bullet is loaded into the same case as the service ammunition and is distinguished by special markings. A larger calibre of armour-piercing ammunition was developed by the Germans for the 13-mm. anti-tank rifle (see RIFLES). The bullet was of the armour-piercing type and weighed approximately 800 grains, while the cartridge case was of the semi- rimless type with a propellant charge of about 200 grains. This cartridge developed a muzzle velocity of about 2,450 f.s. and was very effective against tank armour. Further developments along this line may be expected in the future.

Ammunition for Rifles. Each country has its standard rifle car- tridge which is of the same shape and size and is manufac- tured in the same manner as the machine-gun ammunition above described. Some of these cartridges are of the rimmed while others are of the rimless type. The standard calibres vary from -25 in. to 32 inch. Various other types have been developed for guard, test, and training purposes, such as the blank, dummy, guard, high-pres- sure, and gallery-practice cartridges.

Ammunition for Pistols. The ammunition used in various countries in automatic pistols is very similar, and a description of the manufacture of the United States type may be considered to be representative of all others. This cartridge consists of a drawn brass case with a primer inserted in its head. The bullets, as a rule, have jackets made from drawn gilding metal or some other suitable material. The manufacture of the cartridge case and bullet-jacket follows, in general, the process outlined for the manufacture of the rifle-cartridge components except that the number of operations is considerably reduced. The bullet is -45 calibre, weighs 230 grains and has its jacket tinned and filled with a core of lead hardened with about 2 % of antimony. The cartridge cases are all of the rimless type and have a small cannelure located on the cartridge case in such a position as to prevent a bullet from being pushed back into it. All pistol ammunition is loaded to give low velocities as compared with rifle ammunition. Calibre -45 cartridge, used by the United States, has a muzzle velocity of 800 f.s. and develops a maximum pressure of 16,000 Ib. per sq. inch. In addition to the pistol cartridges of the service type, there are blank and high-pressure cartridges for in- structional and testing purposes. The ammunition made for auto- matic pistols of smaller calibre, used by travellers, police and others, is in principle similar to that of the heavier -45 pistol. (W. L. C.)

AMUNDSEN, ROALD (1872- ), Norwegian polar explorer, was born at Borge, Smaalenene, Norway, July 16 1872, the son of a shipowner. He was educated at Christiania and afterwards studied medicine for two years. Later, however, he went to sea, and from 1897 to 1899 served as mate on the " Belgica " with Capt. Adrien de Gerlache's Antarctic expedition. In 1901-2 he made an expedition to the Arctic regions which resulted in some valuable observations, and from 1903 to 1906 was in command of the " Gjoa " on its voyage through the north-west passage between the Arctic and Pacific oceans (see 21.953). The " Gjoa " made a second Arctic expedition between 1910 and 1912. To- wards the end of 1910 Amundsen started in Nansen's famous ship, the " Fram," for the Antarctic regions. The polar con- tinent was crossed under good conditions, the weather being excellent, while the arrangements for food and transport worked without a hitch. The South Pole was reached between Dec. 14 and 17 1911, the Norwegian party thus outstripping by about a month the British expedition led by Capt. Scott (see ANTARCTIC REGIONS). In June 1918 Amundsen left Norway in the " Maud " with the intention of drifting across the Arctic ocean, but at the end of 1919 was forced to abandon the attempt (see ARCTIC REGIONS). Capt. Amundsen has published The Norlh-West Passage (1907), and The South Pole (1912), and has received many honours from learned societies.

ANAESTHETICS (see 1.907). In connexion with the progress made in 1910-20, it is somewhat remarkable that the agents for producing general surgical anaesthesia which were the first to be introduced, that is, nitrous oxide gas, ether and chloro- form, not only remained in general use, but actually provided in greater part for the requirements of modern surgery. " Regional " anaesthesia, or analgesia as some prefer to call it, had, however, in part supplanted " general " anaesthesia. It consists in abolish- ing sensation in a restricted part of the body without affecting consciousness; it is effected by " blocking " the conduction of sensation through the nerves supplying the area concerned by applying to them a solution of a drug similar in constitution to cocaine, or by injecting this solution into the lower part of the spinal canal and so blocking the sensory fibres in the nerve roots and in the spinal cord itself. Regional anaesthesia has, however, as yet only a limited application, for although adopted as a con- venient routine measure in some classes of cases and types of patients, yet it has been found by experience to have certain limitations, and in the case of spinal anaesthesia certain dan- gers. Many persons, moreover, prefer the blissful ignorance of a general anaesthesia to full consciousness, and passive submission to a trying ordeal, even when they are deprived of sensation and when the sight of the operation is hidden from them.

General anaesthesia produced by the inhalation of a gas or vapour remains the routine procedure. The use of non-volatile drugs, such as morphia or hedonal, introduced by the mouth or by subcutaneous or intravenous injection, is not readily subject to control; once introduced these substances remain in the body until slowly excreted by the kidneys; the dose can be increased but it cannot be decreased, and herein lies a danger. Inhalation anaesthesia on the other hand is susceptible of the most delicate adjustment to requirements. The pulmonary route is adapted anatomically to meet the vital requirements of the absorption and excretion of the blood gases, oxygen and carbon dioxide, and is hence perfectly adapted for the passage to and from the blood of other gases and vapours. The amount of a vapour absorbed by the blood and the rapidity of its absorption are both propor- tional to its concentration in the atmosphere inhaled into the lungs 1 so that the task of the anaesthetist is mainly one of adjusting the strength of the vapour according to the result which is desired. So also the amount which has been introduced into the blood can be rapidly reduced; it is partially exhaled on diminishing the strength of the vapour presented to the blood, and it becomes totally exhaled on withdrawing the vapour entirely from the inhaled atmosphere. This facility of the adjustment of anaes- thesia is not shared by any other method, and it appears likely to sustain inhalation anaesthesia in its present predominant position for some time to come.

1 In the case of chloroform there is a deviation from the laws of the solution of vapours, but this is negligible at the low concentra- tions employed for anaesthetic purposes.