Page:EB1911 - Volume 21.djvu/734

 1898, the mean mortality among the inoculated was 1·3%; among the uninoculated 13·2%. At Daman the mortality was—inoculated 1·6%, uninoculated 24·6%; at Dharwar, inoculated 1·2%, uninoculated 5·2%. In all these cases the numbers dealt with were large and the test fair.

Simpson, in The Practitioner (Dec. 1906), gives an analysis of the results of Haffkine’s serum inoculations as follows:—

In Poona, out of 5595 uninoculated cases the incidence was 6·8%, while in 1500 inoculated cases it was only 0·33%. Klein also prepares a new prophylactic from the dried organs of a guinea-pig, and one of the most interesting experiments is that of Strong (Archiv für Schiffs- und tropische Hygiene, April, 1906), who uses for producing immunity in man a living virulent culture of the bacillus pestis. He immunized 40 persons without mishap and with no more unpleasant results than those occurring after vaccination. Inoculation protects against attack, and greatly modifies the illness when it fails to protect. How long the protection lasts has not been determined, but it appears to be several months at least.

The main authorities for the researches into plague are in the official reports of recent years from India and elsewhere. See generally W. J. Simpson, A Treatise on Plague (1905).

PLAICE (Pleuronectes platessa), a species of flat-fish, common on the coasts of northern Europe from Iceland to the Bay of Biscay. It is readily recognized by the yellow or orange-coloured spots which are placed in a row along the dorsal and anal fins, and scattered over the body. The eyes are on the right side, and the teeth in the jaws compressed and truncate. The scales are minute and smooth. Plaice, like other flat-fishes, prefer a sandy flat bottom to a rocky ground, and occur in suitable localities in great abundance; they spawn early in spring, and are in finest condition in the month of May. Individuals of seven or eight pounds weight are considered fish of large size, but specimens of double that weight have been caught.

 PLAID (Gael. plaide, Ir. ploid, usually taken to be derived from Gael. peall, sheepskin, Lat. pellis, skin), an outer garment, consisting of an oblong piece of woollen cloth, which has formed the principal outer part of the costume of the Highlanders of Scotland. The wearer wrapped himself in the plaid, the lower portion, reaching to the knees and belted, forming the kilt. Later the lower portion was separated, being called the phili beg, the plaid being used as a covering for the shoulders and upper part of the body. The plaids were usually of a checked or tartan pattern. The word is thus used of any cloth made with such a pattern. “Shepherd’s plaid” is a cloth with a chequer of black on a white ground.

PLAIN (O. Fr. plain, from Lat. planum), a level surface; hence in physical geography a tract of country generally quite flat or comparatively so (see ). The adjective “plain” signifies “level,” and thence smooth, clear, simple, ordinary, &c.

PLAINFIELD, a city of Union county, New Jersey, U.S.A., about 24 m. W. by S. of New York City. Pop. (1910 U.S. census), 20,550. It is served by the Central Railroad of New Jersey and by electric lines connecting with neighbouring towns. It is situated for the most part on a plain; north-east are heights occupied by the suburb of Netherwood, and north in Somerset county, on the slope of the first Watchung Mountain, is the borough of North Plainfield (pop. 1910 U.S. census, 6117), which forms with Plainfield virtually a single residential and business community. Plainfield is one of the most attractive residential suburbs of New York. The city has an excellent public school system, a good public library, with an art gallery and museum. The Muhlenberg hospital, club houses and a driving track are features of the city. The value of the factory products increased from $2,457,454 in 1900 to $5,572,154 in 1905, or 46·6%. Plainfield was settled in 1684, but it was not until 1755 that the first frame house was erected. In 1760 a grist mill was erected, and for several years the place was called Milltown. The township of Plainfield was created out of Westfield township in 1847, and in 1867 Plainfield was chartered as a city.

PLAIN SONG, or (Gregorian Music; Lat. cantus planus; Ital. canto gregoriano; Fr. plain chant), a style of unisonous music, easily recognizable by certain strongly marked characteristics, some very ancient fragments of which are believed to have been in use under the Jewish dispensation from a remote period, and to have been thence transferred to the ritual of the Christian Church.

The theories advanced as to the origin of this solemn form of ecclesiastical music are innumerable. The most widely spread opinion is that the older portion of it originated with the Psalms themselves, or at least sprang from the later synagogue music. Another theory traces the origin of plain song to the early Greeks; and the supporters of this view lay much stress on the fact that the scales in which its melodies are composed are named after the old Greek “modes.” But, beyond the name, no connexion whatever exists between the two tonalities. Less reasonable hypotheses attribute the origin of the plain song to the Phoenicians, to the Egyptians, to the early Christian converts, and to the musicians of the middle ages.