Page:The New International Encyclopædia 1st ed. v. 15.djvu/393

PARASITE. PARASITE, Tlaxt. Tlie plant kingdom prest-nt-- abundant illustrations of parasitism, Irom the lowly bacteria to such complicated flowering plants as the mistletoe and dodder. A member of the immense group of fungi must al- ways be either a saprophj-te (q.v. ) or a parasite, and some entire groups have adopted the latter habit, the most disas- trous of the plant dis- eases being due to fun- gous parasites. The po- tato rot and graperine mildew are caused by members of the Perono- sporales. (See Phtco- MTCETES.) The Ustila- ginales (q.v.) are re- sponsible for smut, and the TL'redinales ( q.v. ) for rusts. Some of the leaf- curls are caused by an Ascomycete, and certain important blights and wilts by bacteria. Some very characteristic dis- eases of insects are the

Fig. 1. DODDEE iCnscata) result of fungous para- PABA6ITIC OS i HOP STEM. .. t „ „„„ ♦!,„ Sites from among the

Phycomycetes (q.v.) and Ascomycetes (q.v.). The adaptations developed by many of these parasites to adjust themselves to their hosts are remarkable, and lead to some very complex life histories. A life of parasitism appears to result in sexual degenera- tion ( see Fungi i, so that, associated with remarkable spe- cialization of vege- tative regions, there is in a number of groups the entire loss of sexuality. There are also some remarkable p a r a - .sites among the flow- ering plant.*, the dod- der ( Fig. 1 ) being an extreme example of complete depend- ence upon its host, the root disappear- ing, the leaves being mere scales, and the flowers much re- duced. Other plants have well-developed green leaves, and yet always grow with their roots or other parts connected with some host which supplies certain of their wants. Among these may be mentioned the mistletoe (Viscum), Euphrasia, and Pedicularis. the first-named probably depending upon its host for almost all the water that comes to it. Parasites establish relations with their hosts generally by sucker-like structures, called hau.s- toria (q.v.), or, as in the fimgi, through delicate processes which pierce the cell walls (Fig. 2). See also Sr»Blosis.

PARASITIC DISEASES. An important subdivision in the cl.issification of disease. (See XosoLOGT. ) In these diseases certain morbid conditions are induced by the presence and vital <iy^

Fig. 2. DIAGRAM OF FrXGrs PARASITIC IS THE TISSrE OF THE HOST PLA.VT AND FORMING SPORES ABOVE THE SCRFACE.

activities of various low forms of animal ■^r vegetable life, which have found lodgment n;. subsistence in some tissue or organ, or upon S"!;.- surface of the body of man or animals. Even plants are not exempt from disorders of this nn ture. See Pabasite, Plaxt. The vegetable microorganisms which cause dis- ease are far more numerous and important than the animal, but are as yet less perfectly under- stood. They may be divided into three classes: (1) the Blastomycetes or yeast fungi: (2) the Hyphomycetes, or molds; and (3) the Schisomy- cetes or bacteria.

( 1 ) The yeasts are important only as causes of fermentation. One member of the family, however, is pathogenic, and grows upon the mu- c-ous membrane of the mouth and throat. This is the Oidium albicans, and the disease it gives rise to is called thrush (q.v.). Yeasts are common in the stomach, being introduced with the food, and are found in diabetic urine.

(2) The pathogenic molds are found upon the surfac-e of the body, since they require free oxygen for their growth. They are responsible for many skin diseases. Favus ( q.v. ) is c-aused by the Anchorion Schonleinii. Pityriasis rersi- color, also called chloasma, is caused by the iliscrosporon furfur. Actinomycosis (q.v.) is due to infection by the ray fungus (aetino- myc-es). lladura foot is a serious disease, occ-ur- ring in the feet of natives of India, and was shown in ISGl by Carter to be due to a fungus — Chionyphe Carteri.

( 3 I The Sehizomyeetes or bacteria are by far the most important and interesting of the vege- table parasites. They penetrate every tissue of the )>ody and are known to be the cause of most of the specific febrile diseases, and are suspected to be the cause of others. The study of these organisms has almost reached the dignity of a separate science. See Bacteria.

PARATOLOU). See Tr^EEcrux.

PARAY-EE-MONIAX, pa'ra'-1c-m6'nyal'. A town in the Department of SaOne-et-Loire, France, on the Bourbince. 32 miles northwest of ilacon (Map: France, L 5). Its Benedictine abbey, foimded in 073, contains the tomb of Marguerite Marie Alacoque (q.v.). The revela- tions said to have been made to her here greatly stimulated the devotion to the Sacred Heart of .Jesus ( see Sacred Heart of .Tesps. Feast op THE), which has been so marked a feature of Roman Catholicism in the last two centuries. Paray-le-Monial has consequently become a popu- lar pilgrimage centre, and large numbers, even from America, visit it annually. Population, in 1901. 4362. For an account of the apparitions, consult Bougand, Bistoire dc la bienheureuse Marguerite Marie (Paris, 1894),

PAR'Cffi (Lat., fates; connected with parere, to bring forth, hence originally Parca, a god- dess of childbirth: later associated by popular etvmology with pars, part, identified with the Gk. Mo'ifM, Moira, and then tripled into three Parca to correspond to the three Moi^xw, or Fates). The name given by the Roman poets to the Greek iloirse. or goddesses of fate. They have no place in Roman worship, though the name appears in Gallic territory applied to Cel- tic divinities, who are also called Fati (mascu- line) or Fatae (feminine). In the poets they