ORGANIC ELEMENTS. 47 



19. Arsenic. It was asserted by M. Orfila, that arsenic exists natu- 

 rally in the human body; and that it is a normal constituent of human 

 bones. Subsequent experiments, however, performed by M. Orfila 

 himself, have shown that there was fallacy in his first observations. 1 



ORGANIC ELEMENTS, proximate principles or compounds of organ- 

 ization, are combinations of two or more of the elementary substances, 

 in definite proportions. Formerly, four only were admitted gelatin, 

 fibrin, albumen, and oil. Of late, however, organic chemistry has 

 pointed out others, which are divided into two classes, first, those that 

 contain nitrogen, as albumen, gelatin, fibrin, osmazome, mucus, casein, 

 urea, uric acid, red colouring principle of the blood, yellow colouring 

 principle of the bile, &c.; and secondly, those that do not contain azote, ' 

 as olein, stearin, the fatty matter of the brain and nerves, acetic, 

 oxalic, benzoic, and lactic acids, sugar of milk, sugar of diabetes, pi- 

 cromel, colouring principle of the bile, and that of other solids and 

 liquids, &c. 



a. Organic JElements that contain Nitrogen. 



1. Protein. Modern researches appear to have shown, that tlie 

 chief proximate principles of animal tissues, and those that have been 

 regarded as highly nutritious among vegetables, have almost identically 

 the same composition ; and are modifications of a principle to which 

 Mulder its discoverer gave the name Protein. If animal albumen, 

 fibrin, or casein, be dissolved in a moderately strong solution of caustic 

 potassa, and the solution be exposed for some time to a high tempera- 

 ture, these substances are decomposed. The addition of acetic acid 

 to the solution causes, in all three, the separation of a gelatinous trans- 

 lucent precipitate, which has exactly the same character and composi- 

 tion, from whichsoever of the solutions it is obtained. It may be pro- 

 cured, too, from globulin of blood, and from vegetable albumen. 2 



The chemical relations of protein, especially in regard to oxygen, 

 are full of interest. The products of- its oxidation, binoxide and trit- 

 oxide of protein, occur constantly in the blood. They are formed in 

 the lungs from fibrin ; which, in a moist state, possesses the property 

 of absorbing oxygen. Fibrin, oxidized in the lungs, is, according to 

 Mulder, the principal if not the only carrier of the oxygen of the 

 air in the blood to the tissues ; and it is from this substance especially, 

 that the secretions are formed. In inflammatory conditions, a much 

 larger quantity of protein in an oxidized state is contained in the blood 

 than in health ; and this, according to Mulder, gives occasion to the 

 bufly coat. 3 



The following substances may be regarded as modifications or com- 

 binations of protein. They are composed of it and of a small quantity 

 of phosphorus, or of sulphur, or both. 4 



1 Rapport de 1'Academie Royale de M6decine, Juillet, 1841; Taylor's Medical Jurispru- 

 dence, by Dr. Griffith, p. 133, Philad., 1845; and Simon, Animal Chemistry, Sydenham Soc. 

 edit., p. 4, Lond., 1845, or Amer. edit., Philad., 1845. 



9 Liebig, Animal Chemistry, Gregory's and Webster's edit, p. 100. Cambridge, 1842. 



3 Simon's Animal Chemistry, Sydenham Soc. edit., p. 12, London, 1845; or American edit., 

 Philadelphia, 1845. - Henle, op. cit., p. 31. 



