.# 



17 



of an equal volume of saturated solution of ammonium sul- 

 phate. They comprise [a) serum-globulin of blood-plasma, 

 lactoglobulin of milk, myoglobulin, myosin, and musculin of 

 muscle; (&) myosinogfen of muscle, a peculiar proteid, having 

 properties like both albumins and globulins ; (c) fibrinogen, 

 differing from other globulins in being precipitated from its 

 solution by an equal volume of saturated solution of sodium 

 chloride and by forming fibrin when acted on by the fibrin 

 ferment ; and (d) vitellin differs from globulin in not being 

 "salted out" by sodium chloride. Ova vitellin of egg-yolk 

 and crystallin of the lens of the eye are vitellins. 



12. Take a small portion of the yolk in a test tube and 

 shake thoroughly with ^ tube of ether ! ! for several minutes. 

 Let settle. Carefully pour off the ether into evaporating dish 

 and repeat several times till residue is colorless or nearly so. 



(a). Let the substance in the dish evaporate till the odor 

 of ether is all gone. What is the substance? Pour a little of it 

 in water and note results, also after placing a drop on a piece 

 of paper. 



(b). Transfer the residue in test tube to watch glass and 

 let dry thoroughly. Divide into two portions. Place portion 

 (1) in a test tube, fill tube }6 full of water and shake thor- 

 oughly for five or ten minutes. Does the substance dissolve ? 

 Let settle, pour liquid through " filter " and tqst it for proteid 

 with the biuret test. Save this test and compare with next. 



To the undissolved residue in the tube add a little 10% 

 solution of sodium chloride and shake as before. Result? 

 Filter and apply the biuret test. Result .? Conclusions .? 



13. Place portion (2) in crucible, add a few drops of con- 

 centrated HNO3 and carefully evaporate to dryness high over 

 the flame, charring as little as possible. When dry, let cool. 

 Add a few drops of concentrated HNO3 again and repeat 

 evaporation as above. Now gradually lower crucible into 

 flame and heat until the most of the black substance disap- 

 pears. Let cool, add a little concentrated HCl and heat to 

 boiling. Dilute with an equal volume of water and filter. 

 Divide into four portions. To the first add some potassium fer- 

 rocyanide solution, and to the second some potassium sulpho- 

 cyanide solution. A blue color in the former and a red color 

 in the latter indicates iron. 



