94 THE PROTEIN SUBSTANCES. 



I. Simple Proteins. 



A. True Albuminous Bodies. 



The albuminous bodies are never-failing constituents of the animal 

 and vegetable organisms. They are especially found in the animal 

 body, where they form the solid constituents of the muscles and of the 

 blood-serum, and they are so generally distributed that there are only 

 a few animal secretions and excretions, such as the tears, the perspira- 

 tion, and perhaps the urine, in which they are entirely absent or occur 

 only in traces. 



All albuminous bodies contain carbon, hydrogen, nitrogen, oxygen 

 and sulphur; 1 a few contain also phosphorus. Iron is generally found 

 in traces in their ash. The elementary composition of the different 

 albuminous bodies varies a little, but the variations are within relatively 

 close limits. For the better-studied animal albuminous bodies the 

 following composition of the ash-free substance has been found: 



C 50.5 54.6 per cent 



H 6.5 7.3 " 



N 15.0 17.6 " 



S 0.5 2.2 " 



P 0.42 0.85 " 



O 21.5023.50 " 



The animal proteids are odorless, tasteless, and ordinarily amorphous. 

 The crystalloid spherules (Dotterplattcheri) occurring in the eggs of certain 

 fishes and amphibians, do not consist of pure proteids, but of albuminous 

 bodies containing large amounts of lecithin, which seem to be combined 

 with mineral substances. Crystalline proteids 2 have been prepared 

 from the seeds of various plants, and crystallized animal proteids (see 

 seralbumin and ovalbumin, Chapters V and XII) can be readily pre- 

 pared. In the dry condition the proteids appear as white powders, 

 or when in thin layers as yellowish, hard, transparent plates. A few 

 are soluble in water, others only soluble in salt or faintly alkaline or acid 

 solutions, while others are _ insoluble in these solvents. Solutions of 

 proteids are optically active and turn the plane of polarized light to the 

 left. All proteids when burned leave an ash, and it is therefore ques- 



1 See foot-note 1, p. 80. 



2 See Maschke, Journ. f. prakt. Chem., 74; Drechsel, ibid. (N. F.), 19; Griibler, 

 iUd. (N. F.), 23; Ritthausen, ibid. (N. F.), 25; Schmiedeberg, Zeitschr. f. physiol. 

 Chem., 1; Weyl, 1; ibid., 1. 



