PSALTERY. 



PTOLEMAIC SYSTEM. 



Psalmen,' 1843 ; and Hengstenberg, ' Commentiir iiber die Psalmen,' 

 1843-5. 



PSALTERY, an ancient musical instrument of the harp kind, in 

 use among the Jews, and supposed by Blanchinus to have been the 



b23, nebel (whence va&\a and naitlum), mentioned in several of the 



Psalms. Whether thia instrument was square or triangular, and 

 played on by the finger, or struck by a plectrum, seems doubtful ; the 

 probability is that it took many forms, and was acted on both ways. 

 Blanchiuus makes it square, Luscinius triangular. According to 

 Mersenne, and after him Kircher, the Psalterion, as they denominate 

 this instrument, adopting the Greek term, was in shape a trapezium, 

 and similar to that which is still in use under the name of dulcimer. 

 [DULCIMER.] 



PSEUDERYTHRIN. [LICHENS, COLOURING MATTERS OF.] ' 



PSEUDO-ACETIC ACID. A name given to a peculiar acid strongly 

 resembling acetic acid, said to be occasionally formed during the manu- 

 facture of tartaric acid. 



PSEUDOMORPHINE. [OPIUM, ALKALOIDS OF.] 



PSEUDORCIN. [EHYTHRIC Acm] 



PSEUDOSULPHOCYANOGEN. (Cy 3 HS e ?) When a solution of 

 sulphocyanide of potassium is treated with a current of chlorine, or by 

 boiling dilute nitric acid, an orange-yellow coloured precipitate is 

 obtained which seems to possess the above composition. It is insoluble 

 in water, alcohol, and ether, but dissolves in concentrated sulphuric 

 acid. When heated, it yields bisulphide of carbon, sulphur, and 

 hydromellon : 



3Cy 3 HS. = 6CS, + 68 + SNHCy, 



Uydromellon. 



PSILOMELANE. One of the native forms of binoxide of manga- 

 nese. [MANGANESE.] 



PSORA. [ITCH.] 



PSORI'ASIS is a disease of the skin distinguished by slightly raised 

 red patches of various extent and form, and generally covered with 

 whitish scales. Several varieties of the disease have received different 

 names, according to the form and severity of the eruption in each, and 

 many others, according to the part chiefly or alone affected. The 

 former varieties are Ptoriasil guttata, P. diffuta, P. gyrata, and P. 

 invtterata ; among the latter are P. ophthalmica, P. palmaria, &c. 



Ptoriads guttata is a mild form of the disease, consisting of small 

 red patches two or three lines in diameter covered with very fine white 

 scales. It occurs in various extent on all parts of the body, but most 

 rarely on the face. At first small red spots appear, and soon after 

 present white scales at their centres ; then the spots gradually enlarge 

 and the scales increase in number, till the redness begins to fade at the 

 centre, and as the scales fall off, the skin slowly assumes its natural 

 colour. The eruption is attended by a moderate itching, and by very 

 slight symptoms of general disorder. 



P. di/tua is in every respect a more severe form of the disease. 

 The spots are large and irregular, and often confluent, and covered with 

 thick scaly incrustations. It appears most frequently on the limbs 

 and around the joints, often covering the whole of a limb with one 

 scaly or raw-looking patch, and sometimes occurring at once and with 

 equal severity on several parts of the body. The skin beneath the 

 scales is very tender and irritable ; it often cracks and discharges a 

 thin ichor, which concretes about the fissures, and is attended by con- 

 siderable pain and irritation, and some constitutional disturbance. 

 The eruption often breaks out successively in different parts of the 

 body, so that it is common for the disease to be protracted for several 

 months and even for years. 



P. inveterata is only (as its name implies) a yet less curable form of 

 the same disease. The skin has its whole texture thickened and hard, 

 its surface is covered by a furfuraceous deposit, and in the neighbour- 

 hood of the joints it is often very deeply and painfully cracked. The 

 preceding forms are commonly met with in those who are otherwise in 

 pretty good health; but this rarely occurs, except in those whose 

 constitutions are enfeebled by long disease or want. 



P. 'jyrata is a slight but very rare variety, distinguished by the 

 patches occurring in stripes of a singularly tortuous or serpentine 

 form. 



Of the local varieties of Psoriasis, the most interesting is that which 

 occurs on the palms of the hands, and which, being most frequent in 

 those who work with light powders, and other irritating substances, is 

 commonly called bakers', or bricklayers', or washerwomen's itch. 



Psoriasis, in all its forms, is difficult of cure. The general con- 

 dition of the health being corrected by the means that in each case 

 seem appropriate, the remedy which is most frequently successful in 

 cases of long standing is arsenic, in the form of from three to five drops 

 of the Fowler's solution, three tunes a day, for an adult. Active 

 purging is also often useful, especially in recent cases and in young 

 subjects. Another good remedy is tincture of cantharides, in doses of 

 from three to five drops (for an adult) in water once or more in the 

 day ; but the effects of both this and the arsenic require to be carefully 

 watched during their administration, and they must be discontinued as 

 loon as they appear U> produce auy sickness or heat in the stomach. 



The arsenic should be taken at meals, if not it is more likely to 

 produce sickness. In addition to these, various other internal means 

 have been ^recommended, as decoctions of dulcamara, mezereon, and 

 orchis, antimony, sulphur, &c. Indeed, in many cases it is found 

 necessary to try one means after another without any rule, till one is 

 found which produces benefit. External remedies are generally of less 

 value than internal. The most approved are vapour and sulphur 

 baths, and ointments or lotions containing very small quantities of 

 nitrate of mercury, or white precipitate, or creasote, or alkalies. These 

 however can only be employed in the later stages of the disease : in 

 the earlier, the mildest fomentations give relief, and all kinds of 

 irritants must be carefully avoided. 



PSYCHE (Vvxh). Apuleius is the first writer who relates the loves 

 of Cupid (Eros) and Psyche (' Metamorph.', lib. iv., v.). According to 

 his account, Psyche, the daughter of a king, was the most lovely 

 creature that the world ever beheld. People nocked from all parts to 

 see her, and neglected the worship of Venus, who became in con- 

 sequence jealous of her, and commanded her son to inspire Psyche 

 with love for some mean creature. Cupid, however, instead of 

 obeying the commands of his mother, became enamoured of Psyche, 

 and made her his wife. She was, however, subsequently deserted 

 by him for disobeying his injunction not to seek to behold his face. 

 Inconsolable at her loss, she wandered through the world in search of 

 him, and after enduring many trials and sorrows was at length re- 

 united to him. Jupiter conferred upon her immortality, and her union 

 with Cupid took place with the approbation of Venus and the other 

 deities. A child was soon afterwards born to them, who was called 

 Pleasure. 



This tale is now commonly regarded as an allegory, representing the 

 union between the divine love and the human soul. It probably had 

 its origin in the Orphean mysteries. The word Psyche signifies in 

 Greek both " soul " and a " butterfly." We frequently find in ancient 

 works of art Cupid pressing Psyche to his bosom in the form of a 

 butterfly. When Psyche is represented with a human form, the wings 

 of the butterfly are usually placed on her shoulders. 



Though Apuleius is the first writer who relates the legend, it is 

 certain that the fable of Eros and Psyche must have been current long 

 before his time, as there are many works of art representing some 

 portion of this subject of a date long anterior to that at which Apuleius 

 lived ; though none probably are prior to the Roman period. 



PSYCHROMETER (\f/uxpos, cold, and pevfov, a measure), a term 

 applied to the wet and dry bulb thermometers used as a HTOBOMETEB. 

 [HYGROMETRY.] 



PTELEIC ACID. An acid of problematical existence said 

 to be produced when mesitic chloral is dissolved in solution of 

 potash. 



PTOLEMAIC SYSTEM. A few words of general explanation 

 constitute all that can be given under this head, and we are not 

 now speaking with particular reference to Ptolemy, but of the astro- 

 nomical part of that system which, founded on early metaphysical and 

 physical doctrines, adopted by Plato and Aristotle, reinforced by 

 mathematical hypotheses drawn from Hipparchus and Ptolemy, 

 received by the Mohammedans and by them imparted to the Christians 

 of the middle ages, was the doctrine universally established in Europe 

 till the 17th century. As a whole it combines the physics of the 

 Aristotelian school, the geometry of Euclid and his successors, the 

 sexagesimal arithmetic of the Greeks, and the astronomy of Hippar- 

 chus and Ptolemy, with some slight additions from later names. The 

 geometry remaius, the arithmetic has been supplanted by the decimal 

 system of the Hindus ; the physics and astronomy stood and fell 

 together ; and as under the words Ptolemaic System the astronomy is 

 particularly meant, we only here notice the physical notions so far as 

 they are connected with it. 



The early separation of perceptible matter into the four elements of 

 earth, water, air, and fire, with observation of the relative places they 

 appear to assume, led to the formation of an elementary system. 

 Earth (and solids generally) sink hi water, while air rises in water, and 

 flame in air. Hence the notion that the mass of the earth is the 

 central body of the universe ; above is a region of water, through which 

 rises that portion of earth on which men and animals live. Above 

 this is a region of airland above this again a region of fire. Nothing is 

 at rest until it arrives at its proper or natural place, and all the motions 

 of a part separated from its whole are rectilinear ; fire rises, and 

 bodies fall, in straight lines. Gravity and levity are only the efforts 

 of bodies separated from their natural places to return to them. 



Above the earth and the elementary zones which encompass it, are 

 other successive zones, called heavens. Each heaven contains an 

 immense crystal spherical surface, to which one of the heavenly 

 luminaries is attached, or would be attached, if it moved uniformly 

 in a circle, as it would then do if the crystal sphere were made to 

 revolve uniformly. But the varied motions of the heavenly bodies 

 made it necessary that smaller orbs should be placed with their centres 

 upon the larger ones, as hereafter noticed, and that the planets should 

 move with the smaller ones. It is hardly to be believed (at least so 

 many think I that Ptolemy and the mathematicians received these orbs, 

 in the physical sense, or as anything but hypotheses for representing 

 the actual motions of the planets; it is certain however that the actual 

 solid, orbs cgn.tin.ued, to be received till_a late period, Copernicus uses 



