THE TRUE ALBUMINOUS BODIES. 457 



On the whole, a man weighing 70 kilograms consists of thirteen elementary 

 substances, namely, 44 kilograms of oxygen, 7 kilograms of hydrogen, 1.72 kilo- 

 grams of nitrogen, 0.8 kilogram of chlorin, o.i kilogram of fluorin, 22 kilograms 

 of carbon, 800 grams of phosphorus, 100 grams of sulphur, 1750 grams of calcium, 

 80 grams of potassium, 70 grams of sodium, 50 grams of magnesium, 45 grams 

 of iron. 



ORGANIC CONSTITUENTS. 



THE PROTEID BODIES OR PROTEIN-SUBSTANCES. 

 THE TRUE ALBUMINOUS BODIES. 



The albuminous or proteid bodies, consisting of C, H, N, O and S, are the 

 fundamental and principal constituents of the animal body, to which they are 

 supplied through vegetable food. They are present in almost all animal and 

 vegetable fluids and tissues, partly in liquid form, partly in more consistent, semi- 

 solid form as constituents of the tissues. Their chemical constitution is unknown; 

 their percentage-composition is described on p. 26. The nitrogen is combined in 

 them in two different ways, in part loosely, in which form it can be separated on 

 treatment with dilute hot potassium hydroxid, with the formation of ammonia; 

 and in part firmly. According to Pfliiger a portion of the nitrogen of the living 

 proteid portions of the body is combined in the form of cyanogen. Also the 

 sulphur in the proteid molecule is combined in part firmly, in part loosely. The 

 loosely combined sulphur can be split off by hot potassium hydroxid as potassium 

 sulphid. With lead acetate it forms lead sulphid. The firmly combined sul- 

 phur can be prepared only after destruction of the albumin. In serum-albumin 

 the proportion of the loosely to the firmly combined sulphur is as 3 to 2 . 



The proteid molecule is exceedingly large, and is probably complex. A 

 small portion of it belongs to the group of aromatic substances (which appear 

 especially in connection with putrefaction) ; the larger portion of the molecule 

 to the series of fatty bodies (in the oxidation of proteids, fatty acids especially 

 develop). Also carbohydrates may appear as decomposition- products, not 

 being entirely wanting in any form of albumin studied by Krukenberg. The 

 decompositions in the process of digestion that are of physiological interest are 

 discussed on p. 304, those occurring in the putrefactive processes on p. 333. 



The proteids form a large group of related substances, which perhaps represent 

 only modifications of the same body. If it be borne in mind that the infant pre- 

 pares from the casein of milk the majority of all the proteids of its own body 

 this last view will be clear. The proteids are generally soluble in water or dilute 

 salt-solutions, but with the exception of the peptones, are incapable of diffusing 

 through membranes on account of the large size of their molecule. They are in- 

 soluble in alcohol or ether. They are in general not crystallizable, so that they 

 can be prepared in a pure state only with difficulty. They rotate the plane of 

 polarized light to the left and in the flame they yield the odor of burned horn. 

 They are transformed into a solid modification, that is coagulated, by heat and 

 the long-continued action of alcohol, and are then insoluble in neutral sol- 

 vents. Coagulated albumin is soluble only (i) in dilute alkalies, alkali-albuminate 

 resulting, having lost a portion of nitrogen and sulphur; (2) in dilute mineral or 

 strong organic acids, acid-albumin (syntonin) developing; and (3) by the process 

 of digestion, albumoses and peptones being formed. By neutralization of alkali- 

 albuminate and acid-albuminate, these substances are rendered insoluble. As a 

 result of long-continued boiling with dilute mineral acids or alkalies, as well as 

 of the action of steam under high tension, the proteids take up water and break 

 up into amido-acids, with the formation of ammonia and hydrogen sulphid; on 

 boiling with alkalies, splitting off also carbon dioxid, oxalic acid and acetic acid. 



Color-reactions: (i) Coagulated and heated with nitric acid proteids are stained 

 yellow xanthoproteic acid. Supersaturation with ammonia makes the color 

 orange. (2) If heated above 60 with Millon's reagent (mercuric nitrate with 

 nitrous acid) a red color results. (3) Boiled with potassium hydroxid, then 

 cooled and copper sulphate added, proteids become deep violet-blue. (4) Concen- 

 trated hydrochloric acid (pure) dissolves them on boiling and produces a violet 

 color. (5) Solid proteids are made blue by sulphuric acid containing molybdic 

 acid. (6) The solution of thoroughly desiccated albumin in glacial acetic acid is 

 made violet by concentrated sulphuric acid and exhibits the absorption-band of 

 hydrobilirubin. (7) lodin may be employed as a microscopic reagent, staining 



