PROTOPLASM 1 1 



The ordinary proteids are built on the same plan as the 

 protamines, but have complex side chains of MONAMIDO 

 ACIDS linked to the hexone bases. 1 



Of these monamido acids perhaps the best known are 



(1) Leucin (amido-caproic acid) C 5 H 10 NH 9 CO.OH. 



(2) Tyrosin, in which amido-proprionic acid is linked 



to an aromatic nucleus. 2 



H NH 2 



c H 4 ] _c_ C C H 



H H 



CLASSIFICATION OF THE PROTEIDS 



(A) Simple Proteids. 1. Native Proteids. These pro- 

 teids, either alone, or combined with certain other sub- 

 stances, are constant ingredients of dead protoplasm, and 

 of the fluid constituents of the body. They are distinguished 

 from all other proteids by being coagulated on heating. 



There are two groups Globulins and Albumins the 

 former characterised by being insoluble in distilled water, 

 by requiring the presence of a small quantity of a neutral 

 salt to form a solution, and by being precipitated from 

 solution by half saturating with sulphate of ammonia. 



2. Proteoses (Proteids with a less complex molecule than 

 albumins and globulins). They may be formed from albu- 

 mins (albumoses) and globulins (globuloses), by the action 

 of superheated steam and during digestion. Under the 

 influence of these agents, the complex molecule splits into 

 simpler molecules and takes up water. 



These proteoses form a series between the original proteids 

 on the one hand, and the peptones or simplest proteids on 

 the other. They may be divided into two classes : 



(a) Those nearly allied to the original proteids Proto- 



1 For the tests for proteids and the methods of distinguishing the individual 

 proteids, see Chemical Physiology, p. 3. 



2 For some elementary facts of organic chemistry necessary for the com- 

 prehension of these details, see Appendix, p. 421 et seq. 



