240 PHYSIOLOGICAL CHEMISTRY 



is thrown down. It may be prepared and its reactions studied 

 if time permits. 



The solid meat residue left after extracting the myosin is 

 known as ' ' muscle stroma. ' ' It contains some coagulated myosin, 

 and probably members of other groups. Test it by the xantho- 

 ,proteic reaction and Millon's test. 



iii. N euro globulins. Two and perhaps three globulins occur 

 in the brain. They may be prepared by extraction with salt solu- 

 tions and occur chiefly in the grey matter and the axis cylinders. 



3. Prolamines. The best known member of this group of 

 alcohol soluble proteins is the gliadin of wheat. 



Two students may work together. To about 50 gms. of flour 

 add in small portions enough water to make a dough. Knead 

 this thoroughly in running water until it is washed free of 

 starch. Press out as much water as possible from the solid 

 residue, which is known as gluten. Add 250 c.c. of 70% alcohol 

 (prepare this by diluting 185 c.c. desk alcohol, 95%, to 250 c.c.) 

 and knead up thoroughly with the hand. Shake often, and allow 

 to stand until the next laboratory period, or extract for an hour 

 on the water bath. Filter off the gliadin solution from the residue 

 which is mainly glutenin. Evaporate the gliadin solution on the 

 water bath. On the residue make the following tests. Test its 

 solubility in water and 10% NaCl. Try the Millon and xantho- 

 proteic tests. 



4. Glutelins. The only member of this group which has 

 been carefully studied is the glutenin of wheat. It may be pre- 

 pared from wheat flour by allowing 0.2% KOH to act on the 

 insoluble residue left after the gliadin has been completely ex- 

 tracted. This alkaline extract is then neutralized with HC1, 

 when the glutenin precipitates. 



5. Albuminoids. These proteins are distinguished by their 

 insolubility in neutral solvents. They form the principal or- 

 ganic components of the supporting framework of the body and 

 of hair, nails, horn, etc. 



i. Keratin. (a) Test the solubility of horn in water and 10% 

 NaCl. 



