132 LECTURE VII. 



well as in acids and alkalies. Solutions of pure albumins are neutral. 

 The albumins also differ from the globulins in their behavior on " salting- 

 out." They are not precipitated when their neutral solution is saturated 

 with sodium chloride. Even saturating the solution with magnesium 

 sulphate solution does not produce precipitation. They are not pre- 

 cipitated by a half-saturated ammonium sulphate solution. In acid solu- 

 tions they are, however, precipitated by saturating with sodium chloride 

 or magnesium sulphate. The albumins, as previously stated, have been 

 obtained in crystalline form. 



The globulins are insoluble in pure water and in dilute acids, but are 

 dissolved by dilute alkalies and neutral salt solutions. They can be pre- 

 cipitated from solution by the addition of water or acids. Passing carbon 

 dioxide through their solution is sufficient to precipitate them. The 

 globulins can, consequently, be easily coagulated. They may be redis- 

 solved, only when freshly precipitated. The globulins act like acids, and 

 turn blue litmus red. They are precipitated by a half-saturated ammo- 

 nium sulphate solution. They are very widely distributed. The serum-, 

 milk-, and egg-globulins are best known. There are, undoubtedly, other 

 groups of closely allied proteins, which are, at present, classified separately. 

 Albuminous bodies, very much like the globulins, have been isolated from 

 various animal organs. Thyreo-globulin * is assigned to this class. It 

 contains a large percentage of iodine. 



The globulin-like proteins present in plant seeds are grouped separately. 

 They act as reserve material for the seeds, often occurring in large masses, 

 and are easily obtainable. 2 They are occasionally found in crystalline 

 form, as has been mentioned, and can often be crystallized. Edestin, 

 the best known of these, occurs in various seeds, and can be dissolved in a 

 five per cent sodium chloride solution at sixty degrees, and recrystallized 

 therefrom. These vegetable proteins all react acid and are insoluble in 

 water; they, however, all dissolve in salt solutions, and can be recovered 

 from these by diluting or acidifying. 



The phytovitellins, also called " vegetable-casein," which have been 

 but little investigated, are proteins obtained from plants, and are provision- 

 ally placed in this class. Some of them contain phosphorus, and should, 

 therefore, preferably, be included with the nucleo-albumins. It has not 

 yet been decided definitely whether this phosphorus is actually a part of 

 the protein molecule, or only an impurity. The latter assumption seems 

 justified, as the method of preparation is crude, and very little effort has 

 been made to purify them. The reserve proteins stored in the seeds of 

 various cereals belong to this class. These substances are partially 

 soluble in alcohol. The gluten-casein of wheat, legumin of the legumes, 



1 A. Oswald: Z. physiol. Chem. 27, 14 (1899); 32, 121 (1901). 



2 Cf. H. Ritthausen: Die Eiweisskorper der Getreidearten, etc., Bonn, 1872. 



