258 P A R PAR are Fort Zeelandia (used as a civil and military prison) j at the north corner, between the town proper and the Combe suburb ; the Government-house, surrounded by a magnificent garden and park ; the town-house, with a tower 100 feet high ; the law courts ; the public hospital, where there is a remarkable betel -nut avenue 50 feet in height ; the Reformed Dutch, Lutheran, Moravian, and Roman Catholic churches; and the Portuguese and Dutch syna gogues. The population, barely 16,000 in 1854, was 20,373 in 1869, and 21,265 in 1878. The Indian village of Paramaribo became the site of a French settlement probably in 1610, and in 1650 it was made the capital of the colony by Lord Willougliby of Parham. In 1683 it was still only a "cluster of twenty-seven dwellings, more than half of them grog-shops," but by 1790 it counted more than a thousand houses. The town was partly burned down in 1821, and again in 1832. PARANA. See PLATE RIVER. PARANAHYBA (PARNAHYBA, or PERNAHYBA), SAO Lrjiz DE, a city of Brazil, the chief port of the province of Piauhy, is situated on the right bank of the important Rio de Paranahyba, near the beginning of its delta. It has a population of about 15,000, and trades in cotton, leather, &c., but its port is little visited by foreign steamers. PARASITISM ANIMAL PARASITISM. THE problems suggested by the occurrence of parasites not only in the intestines or the kidneys but even in flesh and blood, in eye or brain, have occupied alike physician and naturalist from the earliest times. From ancient Egyptian and Jewish sanitary and religious codes we may perhaps infer considerable knowledge of the distri bution and danger of parasites, unclean animals like the pig, rabbit, and dog being peculiarly infested with them. The schoolmen, too, perplexed themselves with quaint hypotheses as to the time and place and mode of the introduction of the parasites of man, while the long per sistence of medioeval myths is evidenced by the " Furia infernalis " of the Systema Naturse. The spontaneous generation of parasites seems never to have been doubted until the commencement of the 18th century, when Redi proved the origin of maggots from eggs of the blow-fly, and Swammerdam announced the similar origin of lice and other insect parasites. Both naturalists, however, opposed the extension of their results to the Entozoa, but the discovery of microscopic animalcules, and the reflexion that these must readily be introduced into the body, induced Boerhaave to suggest the origin of parasites from free-living worms and infusorians. The sexuality and char acteristics of a few Entozoa gradually became better known, while Linnaeus, though little dreaming of their complex form-history, expelled the spontaneous generation theory by the in-so-far fortunate mistake of identifying the free Botlirioceplialus of the stickleback as the young stage of B. latus of man, and certain free Planarians and Nematoids as the young of liver flukes and thread worms. His school vastly increased the hitherto scanty catalogue of known forms, while their exacter knowledge rendered his hypo thesis improbable. The origin of Entozoa from eggs which leave the body of their host, enter new hosts in food or drink, and when developing in other organs than the ali mentary are carried thither by the circulation, was clearly put forward by Pallas, who also revived the early view of inheritance, which had been propounded before by the con temporaries of Leeuwenhoek (then, however, to avoid the apparently insoluble difficulty of tracing the origin of the parasite from its innumerable yet apparently wasted ova). With the enormous labours of Rudolphi and Bremser hel minthology rose to the rank of an important special study, yet tho degeneration of the Linnsean school had nowhere fuller course : observation of faunistic and systematic detail excluded all physiological or morphological research, and the knotty problem of origin was simply cut by a { return to the hypothesis of spontaneous generation. This view seemed supported by the absence of reproductive organs in cystic parasites, and reigned almost undisputed until the accumulation of a new chain of evidence. Of this the main links were the discovery of the ciliated larva of a Trematode (Monostomum) by Mehlis in 1831, of the j Redia or Cercaria stages of the same genus, and of the ! six-hooked embryo of Tsenia by Siebold in 1835, and the renewed study of Bothriocejihalus latus by Eschricht, who maintained that the encysted forms were persistently larval, and that the life history of the Entozoa should be viewed as broadly parallel to that of parasitic insects. Yet in spite of all this, and of the corroborative researches of Valentin, many helminthologists remained obstinate, until these incredible life-histories had been confirmed and treated as so many other cases of the "Alternation of Generations" in the epoch-making work of Steenstrup (1842). Dujardin next observed the wanderings of Afermis, and Siebold those of Gordius; the latter, however, advanced the doctrine that cysts were not larval stages, but mere pathological modifications of those worms which had chanced to "wander" into situations unfitted for their normal life. Meanwhile were commencing the important labours of Van Beneden, who traced the actual development of the cystic parasites of the bony fishes into the tape-worms of the rays and dogfishes which had devoured them, so proving that the transmission of the parasites depended upon the mode of feeding. These results were soon confirmed by Kiichenmeister, who not only transmuted cyst into tape worm by transmission in food, but redeveloped the cystic form by feeding with eggs from the adult tape-worm, thus (1852-53) commencing the modern era of experimental helminthology. Haubner and Leuckart eagerly followed for the same group ; Filippi, Valette, Pagenstecher, and Cobbold .made similar investigations on Trematodes; while Leuckart transferred Penta&tomum from rabbit to clog, and traced the formidable Trichina from pig to man. From this time (1860) the advances of our knowledge have been no longer in principle, though numerous and important, but in detail. To Kiichenmeister, Cobbold, Davaine, and others, but more especially to Leuckart, we owe valuable general works ; to the last the present article is especially indebted. 1 Any discussion of parasitism with its difficulties and wide theoretic bearings should naturally be preceded by an account of the known facts. This would involve the pre paration of two systematic lists, the first enumerating the parasitic members of each animal group, while the second, from the point of view not of parasites but of hosts, would indicate the forms which are infested, stating by what parasites. Of these lists the following scanty outlines must suffice. A. Hat of Parasites, Protozoa (see PKOTOZOA). Amoeboid organisms are occasionally detected in dysentery and kindred diseases; the best known of these is simceba coli. Parasitic Infusoria occur much more fre quently : thus in the paunch of slieep and oxen six species (Oph- ryoscohx, Entodinium, Isotriclta] are constant ; similarly in the lectum of the frog or,; invariably present OpaJina, Nyctothcrns, and L alantidium; while B. coli, iirst described from man, inhabits 1 Sec Leuckart, Diemenschlichen Parasittn, 2 vols., Leipsic, 1863-7G; a second edition (commencing in 1S79) is now in progress as Die J arasiten des Menschen ; Cobbold, Parasites, London, 1871); Kiichenmeister and Xiirn, Die Parasiten d. Menschen, 1881 ; Hivsch, Hmdb. d. hist.-gcogi: I athol., 2U ed., vol. ii., Stuttgart, 1883.
