504 VEGETABLE PROTEIDS. 



1. Vegetable albumill is found dissolved in most juices of plants and closely 

 resembles animal albumin. If the dough of wheat be washed with water, and the 

 starch be allowed to subside, on boiling the supernatant fluid the vegetable 

 albumin is coagulated. 



2. Glutin (vegetable fibrin) occurs in cereal grains, and its peculiar glutinous 

 or sticky characters, when mixed with water, enable it to form dough. From 

 wheat, which may contain as much as 17 per cent., it is prepared by washing away 

 all the starch from the dough with a stream of water. This is best effected by 

 washing the dough in a muslin bag or over a tine sieve. It is elastic, gray, insol- 

 uble in water and alcohol, and soluble in dilute acids (1 HC1 per 1000), and in 

 alkalies. Glutin is a complex substance. If it be boiled with water a sticky 

 varnish-like mass is obtained, glladin (animal gelatin). If this substance is 

 treated with strong alcohol it dissolves, but a slimy body remains undissolved, 

 mucedin. If glutin be digested with alcohol, a brownish-yellow substance, glutm- 

 fibrin (Ritthausen) is extracted from it. 



3. Vegetable casein occurs specially in the leguminosse. It is slightly soluble 

 in water, but readily soluble in weak alkalies, and in solutions of basic calcic 

 phosphate. These solutions, like animal casein, are precipitated by acids or 

 rennet. The varieties of it are (a) Legumin in peas, beans, lentils (Einhof, 1805); 

 it has an acid reaction, is insoluble in water, easily soluble in dilute alkalies, and 

 in very dilute HC1 or acetic acid; (6) the casein-like body occurring in hops and 

 almonds which closely resembles (a), and is called conglutin (Ritthausen). Vegetable 

 casein, like animal casein, is an alkali-albuminate, and is precipitated by the same 

 substances; it is not precipitated by boiling. When long exposed to the air, its 

 solution coagulates with the formation of lactic acid. 



250. (2.) The Albuminoids. 



These substances closely resemble true proteids in their composition and origin, 

 and are amorphous non-crystalline colloids; some of them do not contain S, but 

 the most of them have not been prepared free from ash. Their reactions and 

 decomposition products closely resemble those of the proteids; some of them pro- 

 duce, in addition to leucin and tyrosin, glycin and alanin (amido-propionic acid). 

 They occur as organised constituents of the tissues and also in a fluid form. It is 

 unknown whether they are formed by oxidation from proteid bodies or by 

 synthesis. 



] . Mucin is the characteristic substance present in mucus. It contains no S. 

 That obtained from the sub-maxillary gland contains C. 52 '31, H. 7 '22, N. 1T84, 

 0. 28 '63 (Obolensky). It dissolves in water, making it sticky or slimy, and can be 

 filtered. It is precipitated by acetic acid and alcohol ; and the alcohol precipitate 

 is again soluble in water. It is not precipitated by acetic acid and ferro -cyanide of 

 potassium, but HN0 3 and other mineral acids precipitate it (Scherer). It occurs 

 in saliva (p. 292), in bile, in mucous glands, secretions of mucous membranes, in 

 mucous tissue, in synovia, and in tendons (A. Rollet). Pathologically it occurs 

 not unfrequently in cysts ; in the animal kingdom, especially in snails and in the 

 skin of holothurians (Eichwald). It yields leucin and 7 per cent, of tyrosin when 

 it is decomposed by prolonged boiling with sulphuric acid. 



2. Nuclein (Miescher p. 409) C. 29, H. 49, N. 9, P. 3, O. 22, is slightly 

 soluble in water, easily in ammonia, alkaline carbonates, strong HN0 3 ; it gives 

 the biuret-reaction ; no reaction with Millon's reagent ; when decomposed it yields 

 phosphorus. It occurs in the nuclei of pus and blood-corpuscles (p. 36), in 

 spermatozoids, yelk-spheres, liver, brain, and milk, yeast, fungi, and many seeds. 

 Its most remarkable characteristic is the large quantity of phosphorus it contains, 

 nearly 10 per cent. Hypoxanthin and guanin have been obtained as decomposition 

 products from it (Kossel), 



