In England the earliest known ordinances for the regulation of the craft were drawn up in 1348 and received the approval of the mayor and aldermen. From them we learn that for rounded vessels lead might be mixed with the tin in the proportion of 26 lb to each hundredweight, though this quantity appears to have been found excessive, since in 1351 a pewterer was punished because his alloy contained more than 16 lb to the hundredweight, unless this be a clerical error in the contemporary records of the Pewterers' Company. Articles made of this material were to be known as "vessels of tyn for ever but the alloy soon came to be known as "ley." Another formula, however, authorized in the same document, would appear to have been at that time an exclusively English secret, to which was presumably due the universal recognition of the superiority of the island wares which is so notable a fact in the history of pewter. It was known as fyne peauter " and used for dishes, saucers, platters, chargers, and for all "things that they make square," such as cruets, chrismatories, &c., which owing either to the rough usage they would be submitted to, or to the sharpness of their angles, called for greater toughness in the material. The recipe for this alloy as originally propounded was as much brass to the tin " as it wol receiuve of his nature," but the lack of precision in this perhaps rendered it difficult to distinguish accidental variations from deliberate adulteration, and in 1474-1475 it was resolved that 26 lb of brass must be mixed with every hundredweight of tin. The penalties for infringement of the rules were severe and frequently enforced, but in spite of them alterations and improvements crept in. The chief and perhaps the earliest of these was the addition of a certain proportion of bismuth, or as it was then called "tin glass." When this was first used is not recorded, but by 1561 it was accepted as a matter of course; in 1630 a maker " found in fault for not sufficiently tempering his metal with tin glass "; and in 1653 it was ordered that 3 lb weight of tin glass at least must be mixed with every 1000 lb of tin. Antimony was subsequently introduced-though there is no mention of it in the records of the Pewterers' Company-sometimes alone as in tin and temper (1.6 to 150 parts) and trifle (17 parts to 83 of tin), sometimes with other métals as in hard metal (96 parts of tin, 8 of antimony and 2 of copper), a mixture very closely resembling that still used under the name of " Britannia metal," and in plate pewter (100 parts of tin, 8 of antimony, copper and 4 of bismuth). The wares were originally fashioned in two ways, by hammering or by casting, and the workers in each were strictly differentiated, the former, who worked in fine pewter, being known as Sadware men, the latter who used "ley" as Hollow-ware men. A third class, known as Triflers, from the alloy they were limited to, probably at first only manufactured such small articles of domestic use or ornament as did not definitely fall under either of the other headings, but from an authorized list of wares, drawn up by a committee of Triflers in 1612, it is clear that the barrier between them and the Hollowware men had been largely broken down. Another method of working pewter which seems to have been introduced later, and never followed to any great extent, was spinning, by which the vessel was shaped in a mould on a wheel by the mere pressure of a blunt tool, the softness of the metal allowing of its flowing sufficiently for this purpose.

4 of

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then flourishing in Paris and Bruges, whence during the following century it extended to Augsburg, Nuremberg, Poitiers, Mons and other continental centres. Confined at first to the more wealthy classes, we can trace as time goes on its extension lower and lower in the social scale, until at the end of the 17th century its use was almost universal. Thenceforward its vogue steadily declined. The growing cheapness of glass and chinaware and the invention of more showy metals brought upon it by degrees the fatal stigma of vulgarity, until with very few exceptions its manufacture entirely ceased.

Artistically, pewter was at its best when its makers were least conscious of the art revealed in it, thinking more of the durability and appropriateness to purpose of their wares than of their decorative qualities. Though intentionally ornamental vessels may be found earlier, it was not until the 18th century that the pewterers set themselves to slavishly copying the designs and methods of the silversmiths, whether suitable to their material or not, and thereby undoubtedly hastened their own downfall.

Of recent years pewter has taken its place among the articles sought after by collectors, and its cost has so materially and rapidly increased that the manufacture of vessels, guaranteed of course genuinely antique, bids fair to become once more a paying industry. Unfortunately the various enactments compelling each maker to stamp his ware with a definite touchmark seem at all times to have been very generally evaded or ignored, and experience alone is therefore the only safe guide to distinguishing new from old.

BIBLIOGRAPHY.-History of the Worshipful Company of Pewterers of the City of London, by Charles Welch (London, 1902); Pewter Plate, terers, by L. Ingleby Wood (Morton, Edinburgh, n.d.); Old Pewter, by R. J. L. Masse (London, 1904); Scottish Pewter Ware and Pewby Malcolm Bell (Newnes, London, n.d.); Les Métaux dans l'antiquité et au moyen âge. L'Etain, by Germain Bapst (Paris, 1884); Dictionnaire de l'ameublement et de la décoration, by Henri Havard Histoire du mobilier, by Albert Jacquemart (Paris, 1877); “ Analysis of Roman Pewter," by W. Gowland, Archaeologia, vol. lvi. (1898); Pewter Marks and Old Pewter Ware: Domestic and Ecclesiastical, by Christopher A. Markham (1909). (M. BE.)

PÉZENAS, a town of southern France, in the department of Hérault 33 m. W.S.W. of Montpellier on the southern railway. Pop. (1906), 6432. The commerce in cognac, spirits and wines is so important that the prices current for these at the weekly sales are registered throughout the wine marts of France and Europe. There is a handsome monument to Molière, who lived at Pézenas several years and produced his first plays there in 1655 and 1656. A gateway (15th century) and old mansion of the 15th and 16th centuries are of interest.

Pézenas (Piscennae) was founded by the Gauls. In the 10th century it became the capital of a countship subsequently held by important families including those of Montmorency, Condé and Conti. In the 17th century the town was on several occasions the meeting place of the estates of Languedoc.

PFAFF, JOHANN FRIEDRICH (1765-1825), German mathematician, was born on the 22nd of December 1765 at Stuttgart. He received his early education at the Carlsschule, where he met F. Schiller, his lifelong friend. His mathematical capacity was early noticed; he pursued his studies at Göttingen under Abraham Gotthelf Kästner (1719–1800), and in 1787 he went to Berlin and studied practical astronomy under J. E. Bode. In 1788 Pfaff became professor of mathematics in Helmstedt, and so continued until that university was abolished in 1810. From that time till his death on the 21st of April 1825 he held the chair of mathematics at Halle. Pfaff's researches bore chiefly on the theory of series, to which he applied the methods of the so-called combinatorial school of German mathematicians, and on the solution of differential equations. His two principal works are Disquisitiones analyticae maxime ad calculum integralem et doctrinam serierum pertinentes (4to., vol. i., Helmstedt, 1797) and Methodus generalis, acquationes differentiarum particularum, necnon aequationes differentiales vulgares, utrasque primi ordinis inter quotcumque variabiles, complete integrandi in Abh. d. Berl. Acad. (1814-1815). The former work contains Pfaff's discussion

The Reise nach Madagascar was issued in 1861 (Vienna), with a biography by her son.

The principality of Pfalzburg, of which this town was the capital, originally a part of Luxemburg, afterwards belonged in turn to the bishop of Metz, the bishop of Strassburg and the duke of Lorraine, and passed into the possession of France in 1661. The town was of importance as commanding the passes of the Vosges, and was strongly fortified by Vauban in 1680. The works resisted the Allies in 1814 and 1815, and the Germans for four months in 1870, but they were taken on the 12th of December of that year. They have since been razed.

PFEIFFER, FRANZ (1815–1868), German scholar, was born at Bettlach near Soleure on the 27th of February 1815. After studying at the university of Munich he went to Stuttgart, where in 1846 he became librarian to the royal library. In 1856 Pfeiffer founded the Germania, a quarterly periodical devoted to German antiquarian research. In 1857, having established his fame as one of the foremost authorities on German medieval literature and philology, he was appointed professor of these subjects at the university of Vienna; and in 1860 was made a member of the Imperial Academy of Sciences. He died at Vienna on the 29th of May 1868.

Among the many writings edited by him may be mentioned the Barlaam and Josaphat of Rudolf von Ems (1843), the Edelstein of Ulrich Boner (1844), Die deutschen Mystiker des 14. Jahrhunderts (1845-1857; new ed., 1906), the Buch der Natur of Konrad von Megenberg, a 14th-century writer (1861), Die Predigten des Berthold von Regensburg (1862), and the poems of Walther von der Vogelweide (1864; 6th ed. by K. Bartsch, 1880). Of his independent writings the most important are Zur deutschen Literaturgeschichte, Über Wesen und Bildung der höfischen Sprache in mittelhochdeutscher Zeit, Der Dichter des Nibelungenliedes, Forschung und Kritik auf dem Gebiete des deutschen Altertums, and Altdeutsches Übungsbuch. A biographical sketch by Karl Bartsch is in Uhlands Briefwechsel mit Freiherrn von Lassberg, edited by Franz Pfeiffer (1870).

PFEIFFER. IDA LAURA (1797-1858), Austrian traveller, daughter of a merchant named Reyer, was born at Vienna on the 14th of October 1797. In 1820 she married Dr Pfeiffer, a lawyer of Lemberg, who subsequently incurred official persecution and was reduced to poverty. In her later life Mme Pfeiffer devoted her limited means to travel. In 1842 she visited Palestine and Egypt, and published an account of her journey in Reise einer Wienerin in das Heilige Land (Vienna, 1843). In 1845 she set out to Scandinavia and Iceland, describing her tour in two volumes, Reise nach dem skandinavischen Norden und der Insel Island (Pest, 1846). In 1846 she started on a journey round the world, visiting Brazil, Chile and other countries of South America, Tahiti, China, India, Persia, Asia Minor and Greece, and reaching home in 1848. The results were published in Eine Frauenfahrt um die Welt (Vienna, 1850). In 1851 she went to England and thence to South Africa, intending to penetrate into the interior; this proved impracticable, but she proceeded to the Malay Archipelago, spending eighteen months in the Sunda Islands and the Moluccas. After a visit to Australia, Madame Pfeiffer proceeded to California, Oregon, Peru, Ecuador, New Granada, the Missiones Territory, and north again to the Great Lakes, reaching home in 1854. Her narrative, Meine zweite Weltreise, was published at Vienna in 1856. In May of the same year she set out to explore Madagascar, where at first she

PFLEIDERER, OTTO (1839-1908), German Protestant theologian, was born at Stetten near Cannstadt in Württemberg on the 1st of September 1839. From 1857 to 1861 he studied at Tübingen under F. C. Baur; and afterwards in England and Scotland. He then entered the ministry, became repetent at Tübingen, and for a short time held a pastorate at Heilbronn (1868). In 1870 he became chief pastor and superintendent at Jena and soon afterwards professor ordinarius of theology, but in 1875 he was called to the chair of systematic theology at Berlin, having made his name by a series of articles on New Testament criticism and Johannine and Pauline theology, which appeared in Adolf Hilgenfeld's Zeitschrift für wissenschaftliche Theologie, and by his Der Paulinismus, published in 1873 (2nd ed., 1890; Eng. trans., Paulinism: a Contribution to the History of Primitive Christian Theology, 2 vols., 1873, &c.). Das Urchristentum, seine Schriften und Lehren, in geschichtlichem Zusam. menhang beschrieben was published in 1878 and considerably enlarged for a second edition in 1902 (Eng. trans., 1906). In 1890 appeared The Development of Theology since Kant, and its Progress in Great Britain since 1825, which was written for publication in England. A more elaborate work was his Religionsphilosophie auf geschichtlichen Grundlage (1878; 2nd ed., enlarged, 1883-1884; Eng. trans., from 2nd German ed., The Philosophy of Religion on the Basis of its History, 4 vols., 18861888). "The Influence of the Apostle Paul on the Development of Christianity was the title of a course of Hibbert Lectures given in London in 1885. In 1894 he delivered the Gifford Lectures at Edinburgh, the subject being "The Philosophy and Development of Religion." His later publications included: The Early Christian Conception of Christ (1905), Die Entstehung des Christentums (1905; Eng. trans., 1906), Religion und Religionen (1906; Eng. trans., 1907), and Die Entwicklung des Christentums (1907). He died on the 18th of July 1908, at Gross Lichterfelde, near Berlin. In New Testament criticism Pfleiderer belonged to the critical school which grew out of the impulse given by F. C. Baur. But, like other modern German theologians, he showed a greater disposition to compromise. All his work shows a judicial tone of mind, and is remarkable for the charm of its style.

Pfleiderer's younger brother EDMUND (1842-1902) distinguished himself both in philosophy and theology. He too entered the ministry (1864) and during the Franco-German War served as army chaplain, an experience described in his Erlebnisse eines Feldgeistlichen (1890). He was afterwards appointed professor ordinarius of philosophy at Kiel (1873), and in 1878 he was elected to the philosophical chair at Tübingen. He published works on Leibnitz, empiricism and scepticism in Hume's philosophy, modern pessimism, Kantic criticism, English philosophy, Heraclitus of Ephesus and many other subjects.

PFORTA, or SCHULPFORTA, formerly a Cistercian monastery dating from 1140, and now a celebrated German public school. It is in the Prussian province of Saxony, on the Saale, 2 m. S.W. of Naumburg. The remains of the monastery include the 13th century Gothic church, recently restored, the Romanesque chapel (12th century) and other buildings now used as dormitories, lecture rooms, &c. There is also the Fürstenhaus, built in 1573. Schulpforta was one of the three Fürstenschulen founded in 1543 by Maurice duke, and later elector, of Saxony, the two others being at Grimma and at Meissen. The property of the dissolved monastery provided a good revenue for the new educational foundation, which now amounts to about £15,000 a year. Free education is provided for 140 boys, the total number of pupils being 185. After being in the possession of Saxony, Pforta passed to Prussia in 1815, and since this date the school has been entirely reorganized.

See Coste, Die 400 Pforzheimer (1879); Brombacher, Der Tod der 400 Pforzheimer (Pforzheim, 1886); Stolz, Geschichte der Stadt Pforzheim (Pforzheim, 1901).

PHAEDO, Greek philosopher, founder of the Elian school, was a native of Elis, born in the last years of the 5th century B.C. In the war of 401-400 between Sparta and Elis he was taken prisoner and became a slave in Athens, where his beauty brought him notoriety. He became a pupil of Socrates, who conceived a warm affection for him. It appears that he was intimate with Cebes and Plato, and he gave his name to one of Plato's dialogues. Athenaeus relates, however, that he resolutely declined responsibility for any of the views with which Plato credits him, and that the relations between him and Plato were the reverse of friendly. Aeschines also wrote a dialogue called Phaedo. Shortly after the death of Socrates Phaedo returned to Elis, where his disciples included Anchipylus, Moschus and Pleistanus, who succeeded him. Subsequently Menedemus and Asclepiades transferred the school to Eretria, where it was known as the Eretrian school and is frequently identified (e.g. by Cicero) with the Megarians. The doctrines of Phaedo are not known, nor is it possible to infer them from the Platonic dialogue. His writings, none of which are preserved, were in the form of dialogues. As to their authenticity nothing is known, in spite of an attempt at selection by Panaetius (Diog. Laërt. ii. 64), who maintains that the Zopyrus and the Simon are genuine. Seneca has preserved one of his dicta (Epist. 94. 41), namely that one method of acquiring virtue is to frequent the society of good men.

See Wilamowitz, Hermes, xiv. 189 seq.

PHAEDRA, in Greek legend, daughter of Minos and Pasiphaë. With her sister Ariadne she was carried off by Theseus to Athens, and became his wife. On the way to Eleusis she met Hippolytus, son of Theseus by a former wife (Hippolyte, queen of the Amazons, or her sister Antiope), and fell in love with him. Finding her advances rejected, she hanged herself, leaving behind a letter in which she accused Hippolytus of having made dishonourable proposals. The same story, in the main, is told of Bellerophon and Anteia. It formed the subject of tragedies by Sophocles, Euripides (two, one of which is extant), Seneca and Racine.

PHAEDRUS, Roman fabulist, was by birth a Macedonian and lived in the reigns of Augustus, Tiberius, Gaius and Claudius. According to his own statement (prologue to book iii.), not perhaps to be taken too literally, he was born on the Pierian Mountain, but he seems to have been brought at an early age to Italy, for he mentions that he read a verse of Ennius as a boy at school. According to the heading of the chief MS. he was a slave and was freed by Augustus. He incurred the wrath of Sejanus, the powerful minister of Tiberius, by some supposed allusions in his fables, and was brought to trial and punished. We learn this from the prologue to the third book, which is dedicated to Eutychus, who has been identified with the famous

to Particulo, who seems to have dabbled in literature. The dates of their publication are unknown, but Seneca, writing between A.D. 41 and 43 (Consol. ad Polyb. 27), knows nothing of Phaedrus, and it is probable that he had published nothing then. His work shows little or no originality; he simply versified in iambic trimeters the fables current in his day under the name of "Aesop," interspersing them with anecdotes drawn from daily life, history and mythology. He tells his fable and draws the moral with businesslike directness and simplicity; his language is terse and clear, but thoroughly prosaic, though it occasionally attains a dignity bordering on eloquence. His Latin is correct, and, except for an excessive and peculiar use of abstract words, shows hardly anything that might not have been written in the Augustan age. From a literary point of view Phaedrus is inferior to Babrius, and to his own imitator, La Fontaine; he lacks the quiet picturesqueness and pathos of the former, and the exuberant vivacity and humour of the latter. Though he frequently refers to the envy and detraction which pursued him, Phaedrus seems to have attracted little attention in antiquity. He is mentioned by Martial (iii. 20, 5), who imitated some of his verses, and by Avianus. Prudentius must have read him, for he imitates one of his lines (Prud. Cath. vii. 115; cf. Phaedrus, iv. 6, 10).

The first edition of the five books of Phaedrus was published by Pithou at Troyes in 1596 from a manuscript now in the possession of the marquis of Rosanbo. In the beginning of the 18th century there was discovered at Parma a MS. of Perotti (1430-1480), archbishop of Siponto, containing sixty-four fables of Phaedrus, of which some thirty were new. These new fables were first published at Naples by Cassitto in 1808, and afterwards (much more correctly) by Jannelli in 1809. Both editions were superseded by the discovery of a much better preserved MS. of Perotti in the Vatican, published by Angelo Mai in 1831. For some time the authenticity of these new fables was disputed, but they are now generally accepted, and with justice, as genuine fables of Phaedrus. They do not form a sixth book, for we know from Avianus that Phaedrus wrote five books only, but it is impossible to assign them to their original places in the five books. They are usually printed as an appendix. In the middle ages Phaedrus exercised a considerable influence through the prose versions of his fables which were current, though his own works and even his name were forgotten. Of these prose Anonyversions the oldest existing seems to be that known as the " mus Nilanti," so called because first edited by Nilant at Leiden in 1709 from a MS. of the 13th century. It approaches the text of Phaedrus so closely that it was probably made directly from it. Of the sixty-seven fables which it contains thirty are derived from lost fables of Phaedrus. But the largest and most influential of the prose versions of Phaedrus is that which bears the name of Romulus. It contains eighty-three fables, is as old as the 10th century, and seems to have been based on a still earlier prose version, which, under the name of "Aesop," and addressed to one Rufus, may have been made in the Carolingian period or even earlier. About this Romulus nothing is known. The collection of fables in the Weissenburg (now Wolfenbüttel) MS. is based on the same version as Romulus. These three prose versions contain in all one hundred distinct fables, of which fifty-six are derived from the existing and the remaining forty-four presumably from lost fables of Phaedrus. Some scholars, as Burmann, Dressler and L. Müller, have tried to restore these lost fables by versifying the prose versions. The collection bearing the name of Romulus became the source from which, during the second half of the middle ages, almost all the collections of Latin fables in prose and verse were wholly or partially drawn. A 12th-century version of the first three books of Romulus in elegiac verse enjoyed a wide popularity, even into the Renaissance. Its author (generally referred to since the edition of Névelet in 1610 as the "Anonymus Neveleti ") was long unknown, but Hervieux has shown grounds for identifying him with Walther of England, chaplain to Henry II. and afterwards archbishop of

Palermo.

Another version of Romulus in Latin elegiacs was made by Alexander Neckam, born at St Albans in 1157. Amongst the collections partly derived from Romulus the most famous is probably that in French verse by Marie de France. About 1200 a collection of fables in Latin prose, based partly on Romulus, was made by the Cistercian monk Odo of Sherrington; they have a strong medieval and clerical tinge. In 1370 Gerard of Minden wrote a poetical version of Romulus in Low German.

translated; among the editions may be mentioned those of Burmann (1718 and 1727), Bentley (1726), Schwabe (1806), Berger de Xivrey (1830), Orelli (1832), Eyssenhardt (1867), L. Müller (1877), Rica (1885), and above all that of L. Havet (Paris, 1895). For the

Since Pithou's edition in 1596 Phaedrus has been often edited and

in connexion with the removal of cell débris resulting from any injury. Numbers of phagocytes may be found at work in this direction, for instance in the pus formed within an aseptic abscess. Hence we may regard the phagocytes as acting as the scavengers of the tissues.

In the instances we have been dealing with the phagocytes are chiefly of the class of wandering cells and are brought to the seat of their activity by the blood. In examining any tissue where the process is going on it is seen that the phagocytes have accumulated there in large numbers. They have been attracted to the damaged area. The mechanism which effects this attraction is a chemical one-chemiotaxis. At the seat of the change chemical substances are produced which act upon the phagocytes, causing them to migrate towards the source positive chemiotaxis. Apparently the material dissolving from cell débris can act in this manner. Thus if a capillary tube filled with a tissue extract be inserted under the skin of an animal, within a short time it will be found to be surrounded with numbers of leucocytes, which may also have encroached into the tube itself. As in other instances of chemiotaxis the same chemical stimulus in a higher concentration may repel the cells-negative chemiotaxis. Instances of this are especially frequent in relation to micro-organisms and phagocytes, to which we may now turn. That phagocytes can paralyse, kill and digest many microorganisms is the main fact in Metchnikoff's theory of the nature of immunity. The reaction may be readily studied by injecting a small quantity of a fluid culture of some mildly pathogenic organism into the peritoneal cavity of an animal, and in the course of an hour or so examining a smear from the surface of the omentum, when an abundance of phagocytes enclosing the organism in different stages of digestion will be found. Or we may adopt Leishman's method, in which a few drops of human blood are diluted with saline solution and centrifuged. The layer of white corpuscles is pipetted off, suspended in serum, and a minute drop of a suspension of a pathogenic organism is added. The preparation is then incubated at 37° C. for a quarter of an hour. Upon examining a drop of this mixture a number of bacteria are found within the phagocytes. Thus this attack and destruction of bacteria by phagocytes may take place within the 'body or by cells removed from the body. Whether or no a phagocyte can engulf bacteria is dependent upon a number of factors-partly specific properties of the phagocyte, partly factors varying with the constitution of the body serum. Thus Wright and Douglas, employing Leishman's method, have proved that leucocytes do not take up bacteria freely unless the serum in which they are suspended contain opsonins. They found, for example, that leucocytes taken from a patient suffering from a pyococci infection if suspended in normal human serum take up the cocci abundantly, whereas if the same leucocytes are suspended under similar conditions in the patient's own serum the reaction may be almost absent. Further, leucocytes taken from a normal individual and suspended in the patient's serum are practically inactive, while the same phagocytes in normal serum are very active. Exactly how the substance in the serum acts is undecided, but it has been proved that there are in serum substances which become fixed to bacteria and which render them an easier prey to the phagocytes. This specific opsonin is used up when the bacteria are added to the serum, so that if the bacteria are subsequently removed the serum is no longer active. There is evidence too that there is a multiplicity of opsonins. As to the origin of the opsonins we have no certain evidence. It is suggested that they are a secretion from the leucocytes themselves and that it is an evidence of another and preliminary mode of attack possessed by the leucocyte, viz. the discharge of a secretion from the cell which is to damage or paralyse the bacterium and thus enable the phagocyte to engulf it.

The mechanism of destruction of a bacterium once it has been taken up by a phagocyte is probably, just as in the instance of dead cellular material, one of intracellular digestion. The bacterium before being engulfed is probably inert in most instances, though it may yet prove too strong for the phagocyte. The next stage we can trace is the formation of a vacuole around

the organism, or, if the latter be large, around a part of the organism, and the part thus surrounded quickly shows signs of destruction. For instance, its staining reactions become weaker. When a part only of the organism is surrounded by a vacuole the part thus surrounded soon ceases to stain, while the remaining part stains normally, and we thus have a marked contrast evidencing the two stages.

In the next place we must ask which are the cells possessing phagocytic powers? Leaving apart the cells lining the alimentary tract (because we know practically nothing of their power in this respect) a number of free cells possess amoeboid properties as well as also a number of fixed cells. These latter are attached to certain spots of a tissue, but are capable of throwing out processes which can seize upon particles of foreign matter or even upon certain elements of the same organism. Of this category Metchnikoff distinguishes the nerve cells, the large cells of the spleen pulp and of lymph glands, certain endothelial cells, the neuroglia cells, and perhaps certain cells of connective tissues. All these elements can under certain conditions act as phagocytes, and with the exception of the nerve cells all are of mesoblastic origin. Those of greater importance on account of their greater activity in this respect are the large splenic and lymph cells, the neuroglia cells and certain endothelial cells. With regard to the wandering cells Metchnikoff considers that some are certainly non-phagocytic, for instance the lymphocytes. According to Metchnikoff it is only when these cells become older and have developed a nucleus rich in chromatin and an abundant cell body that these cells develop phagocytic properties. This is the large hyaline leucocyte. The polymorphonuclear and the eosinophil leucocyte are both phagocytes. Metchnikoff therefore divides the phagocytes into two classes-the microphages, comprising the polymorphonuclear and the eosinophil cell, and the macrophages, containing the large hyaline cell, the cell of the splenic pulp, the endothelial cell and the neuroglia cell. From further observation of these cells he concludes that the microphages are chiefly concerned in opposing the micro-organisms of acute infections, whereas the macrophages are chiefly concerned in combating chronic infections. It is the macrophage also which is concerned in removing cell débris, e.g. red corpuscles from a haemorrhage or the red corpuscles of another animal which may have been introduced experimentally.

Metchnikoff and his co-workers have shown that the two principal groups of leucocytes are generally spread throughout the vertebrates. Thus instances of each kind are found even in the lamprey, though here their staining properties are feebler; also cells which show but small differences from the analogous cells of mammals are found in the alligator. (T. G. BR.)

PHALANGER, a book-name applied to the more typical representatives of the group of diprotodont marsupial mammals, including the cuscuses of the Moluccas and Celebes, and the socalled opossums of Australia, and thus collectively the whole family Phalangeridae. (See MARSUPIALIA.)

Phalangers generally are small or medium-sized woollycoated marsupials, with long, powerful, and often prehensile tails, large claws, and opposable nailless first hind toes. They seem in the day to be dull and sleepy, but are alert at night. They live mostly upon fruits, leaves and blossoms, although a few feed habitually upon insects, and all relish, in confinement, an occasional bird or other small animal. Several possess flyingmembranes stretched between their fore and hind limbs, by the help of which they can make long and sustained leaps through the air, like flying-squirrels; but the possession of these flyingmembranes does not seem to be any indication of special affinity, the characters of the skull and teeth sharply dividing the flying forms and uniting them with other species of the non-flying groups. The skull (see fig. 1) is, as a rule, broad and flattened, with the posterior part swollen out laterally owing to the numerous air-cells situated in the substance of the squamosal bones. The dental formula is very variable, especially as regards the premolars, of which some at least in each genus are reduced to functionless rudiments, and may even vary in number on the two sides of the jaw of the same individual. The incisors are