60 MANUAL OF PHYSIOLOGY. 



changing to rosy-red on prolonged boiling, or after stand- 

 ing for some days. 



3. Solution of caustic soda and a drop of cupric sulphate 



solution give a violet color to the liquid. 



4. Acetic acid and boiling give a white precipitate. 



5. Acetic acid and potassium ferro-cyauide give a flocculent 



white precipitate. 



6. Acetic acid and equal volumes of sodium sulphate solution 



give a precipitate on boiling. 



7. With sugar and sulphuric acid they become violet. 



8. Crystals of picric acid added to their solutions dissolve 



and at the same time cause bead-like local coagulations. 



CLASSIFICATION OF ALBUMINS. 



Under the head of the albuminous bodies we find several classes 

 which differ from each other in slight but very important points. 

 The first class may be called 



A. Albumins Proper, or Native Albumins. 

 They consist of: 



1. Egg-Albumin, which does not occur in the ordinary tissues 

 of the animal, can be procured by filtration from the white of an 

 egg. It makes a clear or slightly opalescent solution in water, 

 from which it is precipitated by mercuric chloride, silver nitrate, 

 lead acetate, and alcohol. It is coagulated by heat, strong nitric 

 and hydrochloric acids, or prolonged exposure to alcohol and ether. 



2. Serum- Albumin, on the other hand, is one of the chief forms 

 of albumin found in the nutrient fluids. 



It differs from egg-albumin in 



(a) Not coagulating with ether. 



(6) The precipitate obtained by strong hydrochloric acid 

 being readily redissolved by excess of the acid. 



(c) Coagulum being more readily soluble in nitric acid. 



(d) Its specific rotatory power being 56, while that of egg- 

 albumin is 35.5. 



(e) If introduced into the circulation, it is not eliminated 

 with the urine as is egg-albumin. 



