CHEMICAL CONSTITUENTS OF BODY AND FOOD. 37 



salts. They are also insoluble in a half-saturated solution of ammo- 

 nium sulphate. They are coagulated by heat. 



The different members of this group are : serum-globulin (para- 

 globulin), and fibrinogen in blood, myosinogen in muscle, etc. 



Paraglobulin is a precipitate that can be formed from blood- 

 serum by diluting it tenfold with water, and passing through it a 

 current of carbon anhydride. A flocculent, and finally a granular, 

 precipitate results, which is the paraglobulin. 



The coagulated proteids are fibrin, myosin, and casein. The 

 coagulation is produced by ferments. 



Fibrinogen is present in the blood, chyle, serous fluids, and 

 transudations. 



Myosinogen is the principal proteid found in muscle. 



5. Peptones. 



In the body peptones are the final results of the action of the gas- 

 tric and pancreatic juices upon the native proteids, and, as peptones, 

 are ready for absorption by the cells. Although formed in large 

 quantities in the stomach and intestine, they are absorbed as soon 

 as formed, since none are left in these organs. Peptones can, how- 

 ever, be produced outside the body by the action of dilute acids at 

 medium temperatures. 



The peptones are soluble in water, not coagulated by the pres- 

 ence of heat, cannot be precipitated by the usual proteid precipitants, 

 and diffuse very readily through membranous tissues. 



Siegfried has recently isolated peptones of a basic character by 

 hydrolysis of albumins with about 12 per cent, of hydrochloric acid. 

 He calls these bodies kyrines. 



Intermediate products between the native proteids and peptones 

 are the proteases. True peptones are not found in the circulating 

 juices of plants, but the product found is very likely proteose. 



The proteoses are only slightly diffusible, they are not coagulated 

 by heat, but can be precipitated. A characteristic feature of their pre- 

 cipitates is that they can be dissolved by heating, but reappear when 

 the solution cools. 



6. Nitrogenous Bodies Allied to Proteids, or Albuminoids, or Sclero- 



proteins. 



Besides the proteids there are other nitrogenous, noncrystalline 

 bodies that are allied to the former, having many general points 

 in common. 



