32 HUMAN PHYSIOLOGY 



Syntonin, alkali albumin, and coagulated egg albumin are also 

 called derived albumins, in distinction from the native albumins. 



The simple proteids of our body are chiefly dissolved 

 in the blood, lymph, and serous fluids, and form the 

 material for replacing the proteid wastes in the tissues. 

 For this purpose, these proteids are continually circulated 

 through the body by means of the blood and lymph and are 

 therefore called circulating proteids, in distinction from the 

 deposited organ proteids. The circulating proteids are also 

 called dead proteids in distinction from the living proteids 

 of the tissues. 



The term " living proteids" originated from the idea that the 

 proteids of the living substance, because of its peculiar reactions, 

 have different chemical properties and constitution from the 

 unorganized proteids. That such a difference exists cannot be 

 doubted, but what the difference is, is not known. 



Recently peculiar phenomena have been observed in the plasma 

 which have been ascribed to the action of the proteids of the 

 plasma. These phenomena, the immuning and bactericidal action 

 of serum proteids upon pathogenetic micro-organisms, cannot be 

 explained by the physical and chemical properties of dead proteids 

 and are therefore regarded as vital phenomena. 



II. Combined proteids are compounds of simple proteids 

 with other complex substances. They give the general 

 proteid reactions. They are precipitated by alcohol and, if 

 the action is continued for a long time, are coagulated by 

 it. They are precipitated by making the solutions weakly 

 acid, but are readily soluble in weak alkalies. 



Although the substances included in this group differ greatly 

 from each other, still they have this in common, that they are 

 present in the tissue cells as organized proteids, or at least origi- 

 nate from decomposing protoplasm. 



In this class belong: 



(i) Compounds of simple proteids and pigments. 



Haemoglobin, the important constituent of the red-blood 

 corpuscle, is composed of globin, a proteid, and haematin, 

 an organic pigment containing iron. No successful analysis 

 of human haemoglobin has been made. Haemoglobin of the 

 dog has the following composition: C 54.57^; H 7.22$; 



