12 VETERINARY PHYSIOLOGY 



Nucleic acid, when decomposed, yields phosphoric acid and a 

 series of bodies called the purin bodies which belong to the 

 class of diureides, and consist of two more or less modified urea 

 molecules linked together by an oxy-acid with three carbons 

 in series (see p. 427). 



(3) Phospho-ppoteins. Other compounds of proteins with 

 phosphorus-containing molecules occur which do not yield purin 

 bodies when decomposed. Of these vitellin, the protein of the 

 yolk of egg, is an example. 



(4) Histones are probably proteins linked to protamine. 

 They occur in the globin which may be separated from blood 

 pigment. They have a basic reaction. 



(5) Glyeo-ppoteins. Proteins are linked with sugar-like 

 substances to form compounds, the best-known example of 

 which is Muein (see p. 23). 



(6) Chpomo-proteins. In the pigment of the blood (Haemo- 

 globin) proteins occur linked to an iron-containing molecule 

 (p. 219). 



(C) Selepo-Protems 



These are substances produced by protoplasm which are closely 

 allied to the proteins Keratin, Collagen, and Elastin. Their 

 nature is considered under the tissues in which they are found. 



