PROTRACTOR 



consists of a series of cells, ar- 

 ranged in at least two layers, and 

 specialised for the performance of 

 various physiological functions. 



The protozoa may be described 

 asspecksof jelly, the largest of them 

 being only just visible to the naked 

 eye. A good example is seen in the 

 amoeba (q.v.) found in the mud 

 of stagnant ponds. Many of the 

 protozoa, as the Foraminifera 

 and the Globigerina, secrete ex- 

 ternal chalky or flinty skeletons or 

 shells, which form the ooze of the 

 ocean depths and the vast de- 

 posits of chalk in hills. Being 

 unicellular or more correctly non- 

 cellular, a protozoon has no organs. 

 The entire body protoplasm is 

 concerned in the assimilation of 

 food and the performance of all 

 the necessary functions of life. 



The protozoa may be divided 

 into four classes. The Bhizopoda 

 are the lowest, and include such 

 animals as the Amoeba, the For- 

 aminifera, and, according to some 

 authorities, the Mycetozoa. The 

 Flagellata possess whip-like pro- 

 cesses, and are often known as 

 Infusorians. The Ciliata are more 

 or less edged with cilia, by means 

 of which they swim and catch food, 

 as the Paramoecium and Vorticella. 

 The Sporozoa reproduce their kind 

 by the production of spores, the 

 contents of which break up into 

 amoeboid young. In their early 

 stages, these are parasitic within 

 the bodies of higher animals, and 

 some give rise to serious diseases, 

 as malaria and yellow fever. See 

 Amoeba; Animal; Infusoria; Met- 

 azoa ; Paramoecium ; Rhizopoda ; 

 Sporozoa ; Volvox ; consult also 

 Protozoa, M. Hartog, vol. I, Cam- 

 bridge Natural History, 1906; 

 An Introduction to the Study of 

 Protozoa, E. A. Minchin, 1912. 



Protractor (Lat. pro, before ; 

 trahere, to draw). Instrument for 

 measuring and laying down angles. 

 The simple protractor consists of 

 a quadrant or semicircle of wood, 

 metal, or some transparent material 

 graduatedalong the arcual edge into 

 degrees. Straight-edge protractors 

 are also used, the graduation lines 

 appearing drawn obliquely from 

 the centre of one edge to points 

 on the other edge. In marine sur- 

 veying a three-arm protractor is 

 used, the middle arm being fixed at 

 the zero of a circular scale, the 

 other two movable for measuring 

 angles each side of the middle arm. 

 See Surveying. 



Proud Flesh. Overgrowth of 

 new tissue during an unhealthy 

 condition of wounds or ulcers. 

 The newly formed cells are pale in 

 colour and are weakly ; they re- 

 quire treatment with dry dressings 

 or rubbing with blue stone. 



6367 



Proudhon, PIERRE JOSEPH 

 (1809-65). French political philo- 

 sopher. Born at Besan9on, July 15, 

 1809, he worked as a printer until 

 1837, when he published his Essai 

 de Grammaire Generate, a philo- 

 logical study. In 1840 appeared his 

 Qu'est ce que 

 la Propriete ? 

 a strong at- 

 tack on the 

 principle o f 

 property, 

 which he de- 

 clared to be 

 theft. Subse- 

 quent works 



were his AvertissementauxProprie- 

 tairos, 1842; Creation de 1'Ordre 

 dans PHumariite, 1843 ; and Con- 

 tradictions ficonomiques, 1846. In 

 1848 he was elected to the Assem- 

 bly, edited the Representant du 

 Peuple, and was imprisoned, 1850. 

 Prosecuted after publishing De la 

 Justice dans la Revolution et dans 

 I'Eglise, 1858, he lived in Belgium, 

 1858-63. A man of high personal 

 character, he died at Passy, Jan. 

 19, 1865. Proudhon is important 

 in socialist thought as a forerunner 

 of Marx. He urged the ideal of ser- 

 vice balancing service in society, 

 and that the ultimate end of gov- 

 ernment was anarchy, i.e. that in 

 the ideal society government would 

 be unnecessary. His ideas were 

 partly crystallised in the suggestion 

 he put forward for a bank of ex- 

 change. The main principle of 

 this was the issue of bank notes 

 against produce handed into the 

 bank. A bank on these lines, how- 

 ever, failed. His collected works 

 were issued, 1867-70, and his cor- 

 respondence, 1875. See Life, C. A. 

 Sainte-Beuve, 3rd. ed. 1873. 



Proust, JOSEPH Louis (1754- 

 1826). French chemist. Born at 

 Angers, Sept. 26, 1754, and edu- 

 cated as an 

 apothecary, 

 he became 

 chief pharma- 

 cist at the Sal 

 petriere, Paris. 

 Afterwards he 

 went to Spain, 

 where ulti- 

 mately he be- 

 came director 

 of the royal 

 laboratory at 



Joseph Proust, 

 French chemist 



Madrid, but was 

 ruined by the Spanish war, the 

 French on taking Madrid destroy- 

 ing his laboratory and collections. 

 He returned to France, 1806, later 

 receiving a pension from Louis 

 XVIII, was elected to the academy 



PROUT 



of science, 1816, and died at Angers, 

 July 5, 1826. Proust discovered 

 grape sugar, 1805, in various natural 

 products, and was the first to prove 

 that the elements combine in a 

 small number of fixed proportions, 

 Dalton afterwards establishing the 

 law of multiple proportions. 



Proustite. In mineralogy, a 

 sulpharsenite of silver. A bright 

 red colour by transmitted light, 

 giving it the alternative name of 

 ruby silver ore, it is found in 

 Saxony, Spain, and other parts of 

 Europe, and in many of the silver 

 mines of N. and S. America. The 

 mineral is named after Joseph 

 Louis Proust. 



Prout, JOHN (1810-94). British 

 agriculturist. Born Oct. 1, 1810, 

 he emigrated to Canada and farmed 

 in Ontario, 1832-42. Returning 

 to London in 1842, he settled in 

 Saw bridge worth in 1861, and 

 established on scientific lines a 

 farm, where he made valuable ex- 

 periments in cereal raising on clay 

 soils, publishing the results of his 

 observations in Profitable Clay 

 Farming, 1881. He died Dec.7,1894. 



Prout, FATHER. Pseudonym of 

 the Irish humorist, Francis Syl- 

 vester Mahony (q.v.). 



Prout, SAMUEL (1783-1852). 

 British painter. Born at Plymouth, 

 Sept. 17, 1783, he studied under 

 John Britton, 

 settled in Lon- 

 don in 1812, 

 and in 1820 

 was elected a 

 member of the 

 Water Colour 

 Society. H i s 

 earlier works 

 were land- 

 scapes and 

 coast scenes, 

 but visits to 

 the European continent in 1818 and 

 1824 stimulated the talent for 

 picturesque architectural subjects 

 by which he acquired his repu- 

 tation. He died at Camberwell, 

 Feb. 10, 1852. 



Prout, WILLIAM (1785-1850). 

 British chemist and physician. 

 Born Jan. 15, 1785, at Horton, 

 Gloucestershire, and educated at 

 Edinburgh, where he took the 

 degree of M.D., he turned his atten- 

 tion to chemistry. In 1815 he pub- 

 lished his paper on atomic weights, 

 in which he first announced that 

 the atomic weights of all elements 

 are exact multiples of that of hydro- 

 gen. He made a special study of 

 the substances found in living 

 organisms, and was the first to 

 obtain urea in a pure form, and in 

 1823 to discover the existence of 

 free hydrochloric acid in the stom- 

 ach. Prout wrote many scientific 

 papers, and died April 9, 1850. 



