162 



PROTEIN. 



1847. Rathke, Abliandl. und Beitrage, 1830. 

 Valentin, Entwickelungsgeschichte, Berlin, 1835. 

 Baer, Entwickelungsgeschichte, 1837. Costs, Em- 

 bryogenie comparee, 1837. Bischoff, Entwicke- 

 lungsgeschichte der Saugethiere und des Menschen, 

 1842. Weber, Zusatze zur Lehre vom Baue der 

 Geschlechtsorgane, Leipsig, 1846. 



MORBID ANATOMY. Bonetus, Sepulchretum,1700. 

 Morgagni's De Sedibus et Causis Morborum, 1760. 

 Hunter on the Venereal Disease, 1788, 2d edition. 

 Baillie's Morbid Anatomy, 1793. Home, Practical 

 Treatise on the Diseases of the Prostate Gland, 1811. 

 Wilson on the Diseases of the Urinary Organs, 1821. 

 Howship on Diseases affecting Urinary Organs, 1823. 

 Lattemand, Observations surles Maladies des Organes 

 Genito-Urinaires, 1825-27. A.mussat, Le9ons sur les 

 Retentions d'Urine Causees, &c. &c., 1832. Guthrie 

 on the Anatomy and Diseases of the Neck of the 

 Bladder and Prostate Gland, 1834. Mercier. Re- 

 cherches sur les Maladies de la Prostate des Vieillards, 

 1836. CarswelVs Pathological Anatomy, 1833-38. 

 Crosse's Pathological Anatomy, vol. ii., Boston, 1839. 

 Coulson, Diseases of the Bladder and Prostate Gland, 

 1840. Civiale, Maladies des Organes Genito-Uri- 

 naires, 1841. Sir Benjamin Brodie on the Diseases 

 of the Urinary Organs, 3d ed. 1842. Rokitanski, 

 Handbuch der Patholog. Anatomie, 1844. Guy 

 on Diseases of the Prostate Gland, 1845. Engel, 

 Entwurf einer Pathologisch Anatomischen Propa- 

 deutik. 1845. Walshe on Cancer. 



CONCRETIONS AND CALCULI. Marcet, An Essay 

 on the Chemical History and Medical Treatment 

 of Calculous Disorders, 2d edition, 1819, Prout, 

 An Enquiry into the Nature and Treatment of 

 Diabetes, Calculus, and other Affections of the 

 Urinary Organs. Cuveilhier's Pathological Ana- 

 tomy, 1828. Sir Asiley Cooper's Lectures, by 

 Tyrrell, 1824-7. Crosse on the Nature and Treat- 

 ment and Extraction of the Urinary Calculus, 1835. 

 Catalogue of Calculi of Royal College of Surgeons, 

 1842. Dr. C. H. Jones on Calculous Concretions of 

 the Prostate ; see Medical Gazette for Aug. 20. 1847. 

 VogeTs Pathological Anatomy, translated by Dr. G. 

 E. Day, 1847. Dupuytren sur les Calculs de la Pros- 

 tate, dans Bull, de la Gal. de Med., torn. vii. p. 135. 



(John Adams.) 



PROTEIN, (from wpwrefo, I am first,) is 

 the name given by its discoverer, Mulder, to a 

 chemical substance of the highest interest and 

 importance ; since it appears to form the basis 

 of by far the greater portion of the bodies of 

 all animals. 



When pure fibrin, of which animal flesh or 

 muscle chiefly consists, is analysed, it is found 

 to be composed of C 40 H 31 N 5 O 12 and a 

 small quantity of sulphur and phosphorus. 

 Albumen, whether obtained from the serum of 

 the blood, white of egg, or any of the albumi- 

 nous tissues of the body, is found also to con- 

 sist of C 40 H 31 N 5 () 12 and a little sulphur 

 and phosphorus. Casein, too, or the curd of 

 milk, yields on analysis C 40 H 31 N 5 O 12 and 

 a little sulphur, differing from the others in not 

 containing any phosphorus. Hence it appears 

 that fibrin, albumen, and casein, are, chemically 

 speaking, almost identically the same ; and 

 that if we were enabled to separate from 

 each the minute portion of sulphur and phos- 

 phorus, we should obtain a compound in 

 every case the same. Such a substance is 

 protein ; so called from its being the initial 

 letter, as it were, of all this class of organic 

 principles. 



I shall first describe it as obtained artifi- 

 cially, together with the changes produced 



upon it by reagents, and afterwards speak of 

 its more common natural modifications, which 

 play so important a part in building up the 

 fabric of organic beings. 



Protein is most readily obtained from the 

 white of egg, which, as is well known, consists 

 of a solution of nearly pure albumen, contained 

 in a delicate network of cellular membrane. 

 This substance should be well beaten up, in 

 order to break the minute cells in which the 

 albumen is lodged, mixed with about an equal 

 bulk of water, and filtered through a linen 

 cloth to separate the cellular matter, which is 

 insoluble in water ; or it may be allowed to 

 stand until this has subsided to the bottom of 

 the vessel, when the clear liquid may be poured 

 off, or removed by means of a syphon. The 

 solution should then be evaporated to dryness 

 on a water bath, the residue pounded in a 

 mortar, and washed successively with alcohol, 

 ether, and dilute hydrochloric acid, by which 

 means it is purified from extractive matters, 

 fat, phosphate of lime, and the other salts with 

 which it is associated. The pure albumen thus 

 obtained is digested for several hours in a dilute 

 solution of caustic potash, at a temperature of 

 from 120 to 130 ; it readily dissolves in the 

 alkaline solution, and the sulphur and phos- 

 phorus are gradually separated, forming sul- 

 phuret of potassium, and phosphate of potash. 

 Acetic acid is now added in very slight excess, 

 when the protein separates in the form of 

 a white flocculent precipitate, which, when 

 washed with water until all soluble matter is 

 removed, and dried at 212, is pure protein. 

 In order to asertain, however, whether the 

 whole of the sulphur is removed, a small quan- 

 tity should be dissolved in potash, and some 

 of the solution boiled in two test tubes, to one 

 of which a drop of solution of acetate of 

 lead is added. They will both become rather 

 brown, owing to the decomposition of the 

 protein; but if any sulphur is present, the 

 portion to which the lead had been added will 

 become, after boiling for a few minutes, much 

 darker in colour than the other, owing to the 

 formation of sulphuret of lead. 



Protein, when dry, is a hard, semitransparent 

 brownish yellow substance, having a good deal 

 the appearance of amber. It is without taste or 

 smell, and when exposed to damp air rapidly 

 absorbs moisture, which may be expelled by 

 heating it to about 220. When further heated 

 it melts, and almost immediately afterwards 

 begins to decompose, leaving a residue of char- 

 coal, which, if ignited for some little time in 

 the air, burns completely away, leaving scarcely 

 a trace of incombustible ash. Protein is in- 

 soluble in water, alcohol, and ether ; it appears 

 to combine with most of the mineral acids, 

 forming compounds which may be considered 

 neutral, some of which are soluble in water, 

 though insoluble in an excess of the acid. 

 Tribasic phosphoric, and acetic acids, how- 

 ever, do not reprecipitate it when added in 

 excess. It combines also with the alkalies, 

 giving rise to soluble compounds, from which 

 the protein may be again separated by the ad- 

 dition of an acid. It may be thrown clown in an 



