CHEMIC COMPOSITION OF THE HUMAN BODY. 17 



3. The blue- violet reaction. A few drops of copper sulphate solution are 

 first added to the protein solution, and then an excess of sodium hydroxid. 

 A blue-violet color is produced, which deepens somewhat on heating, but 

 no further change ensues. 



The proteins found in the animal body, though possessing many features 

 in common, are nevertheless characterized by certain special features which 

 not only serve for their identification, but for their classification into well- 

 defined groups, as follows: 



SIMPLE PROTEINS. 

 PROTAMINS. 



These proteins are derived for the most part from the heads of sperma- 

 tozooids of fish. When subjected to hydrolysis they can be resolved 

 into the diamino bodies, lysin, arginin and histidin of which they constitute 

 about 90 per cent, and a small number of ammo-acids. For the reason that 

 the protamins contain practically but these three amino-bodies they are re- 

 garded as the simplest of all proteins. 



HISTONS. These proteins are a little more complex than the protamins, 

 and less complex than the typical proteins. They are formed in combination 

 with nucleic acid in spermatozoids, in red corpuscles and various tissues. 



ALBUMINS. 



The members of this group are soluble in water, in dilute saline solutions, 

 and in saturated solutions of sodium chlorid and magnesium sulphate. They 

 are coagulated by heat, and when dried form an amber-colored mass. 



(a) Serum-albumin is found in blood, lymph, chyle, tissue fluids, and 

 milk. It is obtained readily by precipitation from blood-serum, after 

 the other proteins have been removed, on the addition of ammonium 

 sulphate. When freed from saline constituents, it presents itself as a 

 pale, amorphous substance, soluble in water and in strong nitric acid. 

 It is coagulated at a temperature at 73 C., as well as by varions acids 

 e. g., citric, picric, nitric, etc. It has a rotary power of 62.6. 



(6) Egg-albumin. Though not a constituent of the human body, 

 egg-albumin resembles the foregoing in many respects. When 

 obtained in the solid form from the white of the egg, it is a yellow 

 mass without taste or odor. Though similar to serum-albumin, it 

 differs from it in being precipitated by ether, in coagulating at 54 C., 

 and in having a lower rotary power, 35.5. 



