CHEMICAL COMPOSITION OF THE HUMAN BODY 31 



and spinal cord have comparatively less proteids, only 8#. 

 The bones contain 14$ (mostly collagen); the skin contains 

 24$ (mostly collagen); the adipose tissue contains only a 

 small amount (hardly 3$) of proteids. 



(/) Classification of Proteids. 



Proteids are classified into: i. Albuminous bodies or 

 simple proteids; 2. Combined proteids; 3. Proteoses; 4. 

 Albuminoids. 



I. Albuminous bodies or simple proteids are the proteids 

 in a more restricted sense of the word (native proteids) as 

 they are found in the albumin (white) of the egg. Jhey are 

 soluble in water or in dilute salt solutions, are levorotatory 

 and give all the precipitations and color reactions. 



In this class belong the albumins and globulins. The 

 albumins contain more sulphur and give a weaker xantho- 

 proteic reaction than the globulins. 



The albumins are soluble in water ; most of the globulins 

 are soluble only in a dilute salt solution. The globulins are 

 therefore precipitated by half saturation with ammonium sul- 

 phate or by complete saturation with magnesium sulphate. 

 The albumins are not so precipitated. The globulins, in 

 distinction from the albumins, are precipitated from their 

 solution by very dilute acids, even by carbonic acid. 



Among the albumins there are serum albumin, egg albumin, lact 

 albumin, muscle albumin. These albumins differ in their solubility, 

 coagulation temperature, and in their specific rotatory power. 



Among the globulins we have serum globulin, egg globulin, fibrin- 

 ogen, myosinogen. From fibrinogen, a constituent of the plasma, 

 the insoluble farin, is formed by the action of the fibrin ferment. 

 Myosinogen, a constituent of muscles, coagulates during rigor 

 mortis, yielding the myosin. The yolk of egg also contains a 

 globulin-like body, vitellin. 



With acids and alkalies, the simple proteids form syntonin 

 (acid albumin) and alkali albumin. These are not coagulated 

 by heat and are precipitated by neutralizing their solutions. 



