110 PHYSIOLOGICAL CHEMISTRY 



of weak alkalies, or the initial action of enzymes on proteins. 

 The resulting substances are called proteans, and are named 

 from the material from which they are prepared, thus edestan 

 from edestin, myosan from myosin, etc. They differ very slightly 

 from unchanged proteins, and undoubtedly only minor rear- 

 rangements in the protein molecule have occurred in their 

 formation. 



Metaproteins. Metaproteins are formed from the proteins 

 by the action of alkalies or acids, either dilute or concentrated. 

 They are sometimes called albuminates. If a very dilute acid 

 or alkali is allowed to act on a protein at body temperature for 

 some time, perhaps a half hour, it is quite evident that some 

 change has taken place in the protein for if the faintly acid 

 solution of the substance is boiled, no coagulation takes place. 

 Both acid and alkali metaprotein, formed by using dilute acid 

 or alkali, will dissolve in a slight excess either of acid or of 

 alkali. If the solution is made exactly neutral, "however, the 

 metaproteins will precipitate. If this precipitate is suspended 

 in water and boiled, it is coagulated, and no longer can be dis- 

 solved by adding dilute alkali or acid. Dissolving alkali meta- 

 protein in acid, or acid metaprotein in alkali does not change 

 these substances into one another. Perhaps acid metaprotein 

 may be changed into alkali metaprotein by longer action of the 

 alkali, but the reverse process surely does not take place. Alkali 

 metaprotein is formed more quickly than is acid metaprotein, 

 and in the former process some nitrogen and sulphur are split 

 off. Acid metaprotein is particularly interesting because it is 

 formed as the first stage in the digestion of most proteins in the 

 stomach. Gastric juice contains hydrochloric acid which forms 

 acid metaprotein from the proteins of the food, thus bringing 

 them into solution. The metaproteins behave in most respects 

 like proteins, and apparently the protein molecule is not ex- 

 tensively altered when they are formed. 



Coagulated Proteins. Coagulated proteins are formed when 

 acid solutions of most proteins are heated to high tempera- 

 tures, when most proteins are allowed to stand under alcohol, or 



