SLUG WORM SMALLPOX 109 back is wrinkled, and the upper tentacles gran- ulated and black at the tips ; the foot is very narrow; it is found almost always with the isopod crustaceans commonly called sow bugs. Other species are described ; they are compara- tively rare in the United States, and by no means so troublesome as in Europe. The com- mon European slug, L. agrestis (Linn.), is small and unspotted, and very abundant and destruc- Slug (Limax agrestis). tive ; they are killed by solutions of tobacco, salt, or other irritants, or by covering a spot infested by them with ashes, lime, fine sand, or any powder which attaches itself to the body and prevents their walking, or they may be arrested by some sticky substance; many are devoured by mammals, birds, and reptiles. SLUG WORM, the common name of the Iarva3 the sawflies, or the hymenopterous insects of the family tenthredinidce. The slug worm described by Prof. Peck in his prize essay (Boston, 1799), and called by him tenthredo cerasi (Linn.), has been placed by Harris in the genus selandria (blennocampa). The fly is black, with the first pair of legs yellowish clay-colored ; the body of the female is about a fifth of an inch long, that of the male a little smaller. They usually appear in Massachusetts on the cherry and plum trees toward the end of May, disappearing in three weeks after lay- ig their eggs singly in incisions on the lower irface of the leaves; the young are hatched two weeks, coming out from June 5 to July according to season; they have 20 short ags, a pair under every segment except the fourth and the last, and are half an inch long r hen fully grown ; in form they resemble small Ipoles, and are covered with a thick slimy matter which has given them the name of slugs ; they also emit a disagreeable odor. They come their full size in 26 days, casting their skin five times, after which they enter the ground, change to chrysalids, and come out flies in 16 ' ays ; they then lay eggs for a second brood, rhich enter the ground in autumn, and appear as flies in the ensuing spring, some remaining unchanged for a year longer. They feed on leaves, and in some seasons have been so nu- merous as to strip trees entirely of their foliage and even cause their destruction; they are eaten by small mammals and birds, and the eggs are destroyed by the larvaa of a tiny ich- neumon fly (encyrtus). The trees may be best preserved against their attacks by showering them with a mixture of whale-oil soap and water, or powdering with ashes or quicklime. SMALCALD (Ger. SchmalMlden), a town of Prussia, in the province of Hesse-Nassau (before 1866 of Hesse-Cassel), 34 m. E. N. E. of Fulda; pop. in 1871, 5,792. It manufac- tures iron, steel, and salt. The Smalcald league was concluded here in 1531, by various Protestant princes and free cities, for mutual defence of their religious and political inde- pendence against Charles V. and the Catholic states of the empire. It was limited at first to six years, but in 1535 new members were ad- mitted at a second convention in Smalcald, and the term was extended ten years, with a reso- lution to maintain an army of 12,000 men. The elector John Frederick of Saxony and the landgrave Philip of Hesse became the leaders of the league, whose war against the emperor (1646-'7) was terminated by the victory of the latter at Muhlberg, April 24, 1547. In 1537 a confession of faith was drawn up in several articles by Luther, known subsequently as the "Articles of Smalcald," which became one of the symbolical books of the Lutheran church. SMALLPOX (variola), a contagious fever, char- acterized by a pustular eruption having a de- pressed centre. The terms variola and pacce first occur in the Bertinian chronicle of the date 961. Variola is derived from the Latin varus, a blotch or pimple, while pox is of Sax- on origin and signifies a bag or pouch ; the prefix small was added in the 15th century. The era commonly assigned for the first ap- pearance of smallpox is A. D. 569 ; it seems then to have begun in Arabia, and the raising of the siege of Mecca by an Abyssinian army is attributed to the ravages made by smallpox among the troops. The new part which Ara- bia under Mohammed and his followers was made to play in history contributed to the rapid propagation of the disease throughout the world. Ehazes, an Arabian physician who practised at Bagdad about the beginning of the 10th century, is the first medical author whose writings have come down to us who treats ex- pressly of the disease ; he however quotes sev- eral of his predecessors, one of whom is be- lieved to have flourished about the year of the Hegira, A. D. 622. Measles and scarlet fever were at first confounded with smallpox, or considered as varieties of it ; and this error seems to have prevailed more or less until Sydenham finally showed the essential differ- ences between them. Boerhaave was the first to insist that contagion is essential to the prop- agation of the disease. The period of incuba- tion, that is, the time that elapses from the moment the patient receives the contagion until it begins to manifest its effect in the initiatory fever, is usually 14 days, though it sometimes varies. During this time there is usually no disturbance of the ordinary health.
