LE SUEUR, JEAN-FRANCOIS. 



LEUWENHOEK, ANTHONY VAN. 



870 



in 1644, and sentenced to be shot as a spy, but some delay having 

 protracted the execution of this sentence, he managed to escape, in 

 1648, and attempted to raise an insurrection in Kent. This having 

 failed, he fled the country, but returned in 1653, hoping to take 

 advantage of the general act of amnesty. Cromwell having taken his 

 part, his hopes were realised, though this circumstance caused him to 

 be eyed with some suspicion by his friends the royalists. After the 

 Restoration he was appointed censor of the press, and in 1665 he 

 brought out a paper called the 'Public Intelligencer." He was devoted 

 to the court, and on the approach of the Revolution of 1688 lost all 

 his appointments. He died in 1704. 



His works consist of a vast number of political pamphlets, besides 

 translations of Josephus, Cicero's ' Offices," Seneca's ' Morals," Eras- 

 mus's ' Colloquies,' ^sop's ' Fables,' Quevedo's ' Visions," &c. He is 

 generally and very justly censured for having used too many vulgar 

 and coarse expressions in his versions of classic authors, but on a 

 reference to Echard's low translation of ' Terence ' it will be found 

 that this fault was not peculiar to L'Estrange. 



LE SUEUR, JEAN-FRANCOIS, a very distinguished French 

 composer, knight of the Legion d'Honneur, and director of the 

 music of the Emperor Napoleon I., waa the descendant of an ancient 

 family, and born in 1766. After having been Maltre de Chapelle of 

 several cathedrals in France, for which he composed a great number 

 of masses, motets, &c., his reputation called him to Paris, where he 

 produced his five grand operas : ' La Caverne," ' Paul et Virginie," 

 ' Tele'maque,' ' Les Bardes,' and ' La Mort d'Adam," all of which 

 display more or less vigour of imagination, grandeur of style, and 

 judgment in execution ; qualities which induced Sacchini to say, that 

 he knew but two Italians who could be compared to him. That M. 

 Le Sueur possessed a strong active mind may be inferred from his 

 compositions; but of this he gave other proofs, as well as of literary 

 talent; hia work on music adapted to sacred solemnities, is highly 

 esteemed ; and a notice by him concerning ancient music, accom- 

 panying the translation of ' Anacreon' by M. Gail, not only ehows 

 considerable learning, but, in the opinion of M. Qinguene, has thrown 

 some new light on that very obscure subject, the music of the Greeks. 



LEUCIPPUS, a Grecian philosopher, is generally regarded as the 

 original proponnder of what has been called the atomic philosophy. 

 The time and place of hia birth are unknown; he was the disciple of 

 Zeno and the teacher of Democritue, and was born, according to 

 Diogenes Laert. (ix. 30), either at Elis, Abdera, or in the island of 

 Helen. None of his writings have come down to us, with the exception 

 of a few fragments of a treatise ' On Mind," which have been preserved 

 by Stobreus. Some account of his philosophical doctrines is given by 

 Diog. Laert, ix., 30 ; Aristotle, ' De Anima/ i. 2 ; Plutarch, ' De 

 PlacitU Philoroph.,' c. xvii., p. fc83, E.; Cicero, 'De Nat. Deor.,' i. 24; 

 Lactautius, 'Divin. Instil., 1 iii. 17; 'De Ira Dei,' c. 10; Fabricii, 

 'Bibliotheca Graeca,' vol. ii., p. 658, 659, ed. Harles; Bayle, 'Diet.'; 

 and the article DEMOCBITUS in this work. 



LEUNCLA'VIUS, JOHN (the Latinised form of his real name, 

 Loewenklau), was born in 1533 at Amelburn, in Westphalia. He was 

 one of the most distinguished scholars of his age ; he was well 

 acquainted with the Latin and Greek languages, the Roman law, and 

 the writings of the fathers, and also with Turkish, which he learnt 

 during hi) residence at Constantinople. He died at Vienna, 1593. 



The most important of the works of Leunclavius are : Editions of 

 Zoeimus, Proeopius, 4c., Basel, 1579 ; Manuel Palaeologus, Basel, 1578; 

 Dion Cassius, 1592 and 1606 ; Xenophon, 1569, Par., 1622, 1625 ; John 

 of Damascus, Basel, 1578 ; and many treatises of the fathers. He also 

 wrote ' Couimentatio de Moscorum bellia adversus finitimos Gestis," 

 in Piatorius's collection of Polish, historians, 1655; ' Musulmanicie 

 Hutorite, libri xviii.,' Frank., 1595; ' Annales Sultanorum Othomani- 

 daram," Frank., 1596, a translation from the German of Gaudier; 'Jus 

 Grscco-Romanum, tun Canonicum quam Civile,' Frank., 1596 ; ' Versio 

 et Notaj ad Synopsim LX. Librorum Baailicon, sou universi juris 

 Romaui et ad Novellas imperatorum," Basel, 1575, Leyden, 1617. 



LEUSDEN, JOHN, was born at Utretcht in 1624. He studied the 

 Oriental languages, and particularly Hebrew, with great success at the 

 universities of Utrecht and Amsterdam. In 1649 he was appointed 

 professor of Hebrew at Utrecht. He died in 1699. Leusden was one 

 of the best Hebrew scholars of his age, though perhaps not equal 

 to the Buxtorfs. Some of his works may still be consulted with 

 advantage. 



The most importantof Leusden's works are : 'Philologus Hebroms," 

 Ut, 1848, 1672, 1695, Amst., 1686; 'Philologus Hebraso-Mixtus,' Ut, 

 1683, to.; 'Philologus Hebrseo-Grajcus," Ut., 1670, &c. (these three 

 volumes contain many curious discussions on the original languages of 

 the Bible, the state of the Hebrew and Greek text, and that of the 

 Septuagint, as well as considerable information on Jewi.-h rites and 

 antiquities); 'Jonas Illustratus,' Ut, 1656; 'Joel Explicatus,' &e., 

 Ut, 1657; 'Scholia Syriaca," 1658-72; 'Onomaaticon Sacrum," 1665; 

 ' CUvU Hebraioa et Philologica Veteris Testamenti," Ut, 1683, a useful 

 book for beginners; 'Clavis Qrasca Novi Testament!,' Ut, 1672; 

 < Compendium Grtecum Novi Testamenti,' Ut, 1674, &c. ; best edition, 

 1762; ' Compendium Biblicum,' Ut., 1674, Halle, 1736; 'Novum 

 Testamentum Grtecum,' Ut, 1675. He also wrote the Preface and 

 Introductions to Athias's ' Hebrew Bible,' Amst. (1661-67), and edited 

 Pool's 'SynopsUCritlcorum' (1684), aad the works of Lightfoot (1699), 



and Bochart (1675, 1692). He published several Manuals of Hebrew- 

 Grammar, which however are almost entirely taken from Buxtorf. He 

 had commenced an edition of the Syriac version of the New Testament, 

 which was published after his death by Schaaf, Leyden, 1708. 



LEUWENHOEK or LEEUWENHOEK, ANTHONY VAN, was 

 born at Delft in Holland in 1632, and does not seem to have had 

 the advantage of a learned education. The skill which he possessed 

 in grinding glasses for microscopes first brought him into notice, and 

 his microscopes were said even to excel those of the celebrated 

 Eustachio Divini. He did not confine his attention however to the 

 mechanical construction of instruments, but made many researches 

 on the minute structure and composition of various animal fluids and 

 solid textures, and he acquired great fame as an anatomist and physio- 

 logist. Dr.DeGraaf introduced him to the notice of the Royal Society 

 of London, and the greater number of his discoveries aud researches 

 were published in the ' Philosophical Transactions ' of that body. His 

 first communication was transmitted to the Hoyal Society by D Graaf 

 in 1673. His contributions to the ' Philosophical Transactions ' became 

 afterwards numerous and important, and amounted altogether to about 

 112 papers, which are included between No. 91 and No. 380 of that 

 work. In 1680 he was chosen a Fellow of tha Royal Society, and he 

 was made a corresponding member of the Academy of Sciences at Paris 

 in 1697. He appears to have passed the whole of his life at his native 

 place, devoting his time to microscopic researches, chiefly relating to 

 anatomy ; and the success which attended his observations is said to 

 have principally arisen from his having paid the most minute attention 

 to the grinding and polishing of tingle lenses, which he always used 

 in preference to the compound microscope. 



The subjects of Leuwenhoek's labours were so numerous, that we 

 can only briefly mention some of the most important of them. Some 

 of the antagonists of Harvey objected to his doctrine of the circulation 

 of the blood on the ground that, if the blood passed directly from the 

 arteries into the veins, it could not nourish the parts through which 

 it flowed. This question was undecided, when Leuweuhoek commu- 

 nicated a memoir to the Royal Society, in which he stated, as the 

 result of his experiments, that, contrary to the opinion of Harvey, the 

 passage of the blood was not immediate from the arteries into the 

 veins. However in 1690, having very carefully re-examined the course 

 of the circulation through the minute vessels of a part with a more 

 perfect microscope, he discovered and clearly demonstrated that the 

 arteries and veins are continuous. He even refused to admit that 

 there is any division between the arterial and venous capillaries, 

 because he said that it is impossible to determine where arteries ter- 

 minate or veins begiu. The latest investigations have proved the- 

 conclusions of this great microscopist to be nearly correct ; for though 

 the transit of the blood from arteries to veins can be observed by 

 means of the microscope in many transparent parts, as the web of the 

 frog's foot, yet the nature of the minute or capillary vessels through 

 which the communication is effected is imperfectly understood. 



At the time when Leuweuhoek made these observations the chemical 

 doctrines reigned in medicine, and all the processes in the animal 

 economy were explained by chemical changes : the blood was said to 

 undergo the process of fermentation. Leuweuhoek triumphantly 

 opposed this hypothesis, objecting to it that, if fermentation took place, 

 bubbles of air would be generated in the vessels, which could never be 

 observed. He also directed his attention to the form of the globules 

 of the blood, which Malpighi bad already discovered. Leuwenhoek 

 stated that they are oval and flattened, and that each is composed of 

 six exceedingly minute conical particles, which separately do not 

 reflect the red colour, but which by their union communicate to the 

 blood the physical properties which it presents. This theory served 

 as the basis of that of Boerhaave on inflammation. Leuwenhoek stated, 

 in proof of his hypothesis, that the red capillary vessels divide into 

 smaller branches, in which the circulation is beyond the influence of 

 the heart, and where the blood appears white because its globules are 

 divided so as to accommodate themselves to the size of the canals 

 through which they pass. Later experiments have shown the fallacy 

 of these ideas on the blood. 



The brain and nerves were also the subjects of his researches. He 

 described the cortical substance as being entirely vascular, and said 

 that the vessels which compose it are five hundred aud twelve times 

 smaller than the minutest capillaries ; and that the globules which, 

 compose the fluid contained in these vessels are thirty-six times more 

 minute than those which form the red blood. Fresh experiments 

 made him change his opinions, aud in 1717 he showed that the brain 

 and nerves are fibrous structures, and that the blood-vessels glide 

 between the fibres which compose these tissues. These observations 

 very nearly agree with those of modern anatomists as to the structure 

 of the brain ; the only part in which Leuweuhoek seems to have been, 

 deficient was in a clear knowledge of the difference of structure between 

 the cortical or grey and the medullary or white parts of the brain. 

 Thus when he discovered that the latter was fibrous, he supposed that 

 the former must be so also ; whereas the cortical substance is composed 

 almost entirely of blood-vessels connected by exceedingly fine cellular 

 membrane, as first stated by Leuweuhoek, and investing, as has been 

 since ascertained by Valentin, small grey globules or granules. It ia 

 now universally agreed that the medullary port of tho brain u 

 composed of libro '. 



