PROTEINE, AND ITS TRANSFORMATIONS. 105 



is further shown by the fact, that from both of them (as well as from various 

 substances used as food, which are furnished by the Vegetable kingdom, 111) 

 an identical substance may be obtained by a simple process. If boiled al- 

 bumen be dissolved in a weak solution of caustic alkali, and the liquid be 

 neutralized by an acid, a precipitate falls down in grayish-white flocks ; this, 

 being collected and washed, is gelatinous, of a grayish colour, and semi-trans- 

 parent; and, when dried, it is yellowish, hard, easily pulverized, tasteless, in- 

 soluble in water arid alcohol, and decomposed by heat without fusing. This 

 substance has been termed Proteine, from an idea that it is the fundamental 

 proximate principle of which Albumen, Fibrine, &c., are modifications. It 

 contains the same proportions of Carbon, Hydrogen, Nitrogen and Oxygen, with 

 Albumen and Fibrine ; but it has been commonly regarded as destitute of their 

 Sulphur and Phosphorus; the most recent investigations of Liebig, however, 

 render it doubtful whether this is the case. According to Mulder (its dis- 

 coverer), its composition may be represented by the formula 40 C, 31 H, 5 N, 

 12 O ; whilst by Liebig it is represented by the formula 48 C, 36 H, 6 N, 14 O. 

 Either of these correctly represents the relative proportions of the elements, 

 as deduced from analysis ; but the formula of Mulder is asserted by him to 

 represent more accurately the combining equivalent of the entire substance, 

 as deduced from the compounds it forms with others. 



a. According to Mulder, Proteine unites with Oxygen in definite proportions, so as to form 

 a binoxide and a tritoxide. These are both produced when Fibrine is boiled in water for 

 some time; the latter being then found in solution, whilst the former remains insoluble. 

 The tritoxide may also be formed by boiling Albumen for some time in water, when it is in 

 like manner taken up in solution ; but the insoluble residue is still albumen. It is further 

 attainable by decomposing the chlorite of proteine with ammonia. In its properties it some- 

 what resembles Gelatine, and has been mistaken for that substance. There is reason to 

 think that this compound really exists as such in the blood; a small quantity of it being 

 formed every time that the blood passes through the lungs, and given out again when it 

 returns to the system ; and a much larger quantity being generated during the inflammatory 

 process, so that it may be easily obtained from the buffy coat by boiling. It is also said to 

 be contained in pus. The binoxide is quite insoluble in water, but dissolves in dilute acids. 

 It may be obtained by dissolving Hair in potash, adding a little acid to throw down the 

 proteine, and then adding a large excess of acid, which precipitates the binoxide. Accord- 

 ing to Mulder, this compound also is produced in small quantity at every respiration; and it 

 enters into the normal composition of several of the animal tissues. These views, however, 

 must still be received with some hesitation. They are liable to the fundamental objection, 

 advanced against them by Liebig; that the binoxide and tritoxide, like proteine itself, contain 

 the sulphur of albumen and fibrine. Still, the production of new and peculiar compounds, 

 by the processes indicated, is an important fact which cannot be overthrown ; whatever 

 may prove to be the case in regard to the ultimate composition of these substances. 



b. One of the most characteristic and important properties of Proteine, is the facility with 

 which it undergoes decomposition, when acted on by other chemical substances, especially 

 by alkalies. If a proteine-compound be brought into contact with an alkali, ammonia is im- 

 mediately disengaged ; indeed the alkaline solution can hardly be made weak enough to 

 prevent the disengagement of ammonia. This is a property, which must be continually 

 acting in the living body ; since the blood has a decidedly alkaline reaction. If either albu- 

 men, or any other proteine compound, be boiled with potash, it is completely decomposed; 

 not, however, being resolved at once into its ultimate constituents, or altogether into simple 

 combinations of them; but in great part into three other organic compounds, Leucin, Protid, 

 and Erythroprotid. Leucin is a crystalline substance, which forms colourless scales, destitute 

 of taste and odour ; it is soluble in water and alcohol, and sublimes unchanged. It consists 

 of 12 Carbon, 12 Hydrogen, 1 Nitrogen, and 4 Oxygen. There is not at present any evi- 

 dence, that it is produced in the living body; but considerable interest attaches to it from the 

 fact, that it may be procured from Gelatine, as well as from Proteine ; a near relationship 

 between these two substances being thus indicated. The other two compounds, Protid and 

 Erythroprotid, are uncrystalline substances ; the former of a straw-yellow, the latter of a red- 

 dish-brown colour ; they belong to the class of bodies which were formerly included under 

 the vague general term of extractive matter; and they bear a strong resemblance to Gelatine, 

 not only in their solubility in water, but also in their chemical composition, as is shown by 

 the following comparison of their formulae : 



