52 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 



experimented with beans; he found the faeces contained as much as 30'3 of the 

 nitrogen of the beans in an undigested condition. Beans thus compare 

 unfavourably with lentils and bread, but even here there is a considerable 

 undigested residue. The investigations of Rutgers l point to the fact that this 

 is due rather to the admixture of vegetable proteids with cellulose and other 

 indigestible materials than to any peculiarity in the proteids themselves. 



The foregoing brief account of the vegetable proteids may be amplified by 

 further consideration of some of the points raised : 



Researches on crystallised vegetable proteids. In 1855, Hartig 2 pointed out 

 the existence of crystallised proteid matter in seeds. Four years later, Maschke 3 

 obtained hexagonal plates of proteid matter by extracting Brazil nuts with 

 water at 40-50 C., and evaporating the filtered extract at 40. Nageli 4 de- 

 signated such crystals as crystalloids. 4Veyl 5 identified the crystals as vitellin. 

 Sachsse, 6 by Maschke 's method, and also by precipitating the aqueous extract 

 by a stream of carbonic anhydride, obtained several preparations of proteid from 

 Brazil nut which he analysed. The precipitate consisted of small discs, 

 not crystals. Schmiedeberg 7 obtained crystalline products from the car- 

 bonic anhydride precipitate by digesting it with magnesia solution at 35 C., and 

 evaporating at the same temperature. Drechsel 8 obtained hexagonal crystals, 

 by submitting the solution containing Schmiedeberg's magnesia compound to 

 dialysis against alcohol, and also by the slow evaporation of a warm sodium 

 chloride solution of the proteid. 9 At Drechsel's suggestion, Griibler 10 applied 

 this method with some modifications to the proteids of squash seed, from which 

 he obtained octahedral crystals ; he obtained lime as well as magnesia crystalline 

 compounds. Bitthausen, 11 by similar methods, obtained octahedra and rhombic 

 dodecahedra from expressed hemp cake, castor-oil seeds, and seeds of Sesamum 

 indicum. Molisch 12 has separated by the use of ammonium sulphate a 

 crystalline proteid (phycocyanin) from the alga, Oscillaria leptotriclia. 

 Vines 13 found that the natural crystalloids, embedded in the ground 

 substance of the aleuron grains, were hexagonal rhombohedra in some plants, 

 and regular tetrahedra in others. 



Some of the details of Vines' work are as follows : 



The aleuron grains of the peony contain an albumose and vegetable 

 myosin ; of the castor-oil plant, an albumose, a myosin, and vitellin ; of blue 

 lupin, chiefly crystalloid vitellin. He classified aleuron grains into 



1. Those soluble in water, albumose. 



2. Those soluble in 10 per cent, sodium chloride solution 



(a) Without crystalloids, soluble in saturated sodium chloride solution, 

 vitellin. 



(b) With crystalloids, insoluble in saturated sodium chloride solution, myosin. 



3. Those partially soluble in 10 per cent, sodium chloride solution. Some of 

 these are crystalloid, some insoluble, some soluble in saturated salt solution. 



Vitellin is the principal constituent of egg yolk, and occurs there in the 

 form of seniicrystalline sphaerules, corresponding to the crystalloid aleuron 

 grains of plants. The proteids described by Valenciennes and Fremy u in the 



1 Ztsc.hr, f. BioL, Miinchen, Bd. xxiv. S. 251. 2 Bot. Ztg., 1855, S. 881. 



8 Journ. f. prali. Chem. , Leipzig, Bd. Ixxiv. S. 436. 



4 Bot. Mitth., Miinchen, 1863, Bd. i. 



5 Arch. f. d. ges. Pliysiol., Bonn, Bd. xii. S. 635 ; Zlschr. f. pliysiol. Chem., Strassburg, 

 Bd. i. S. 72. 



6 "Die Farbstoffe, Kohlenhydrate mid Proteinsubstanz, " Leipzig, 1877, S. 315. 



7 Ztschr. f. pliysiol. Chem., Strassburg, Bd. i. S. 205. 



8 Journ. f. praU. Chem., Leipzig, Bd. xix. S. 331. 



9 See Grubler, ibid., Bd. xxiii. S. 100. 10 Ibid., Bd. xxiii. S. 97. 



11 Ibid., Bd. xxiii. S. 481. 12 Bot. Ztg., 1895, Bd. i. S. 131. 



13 Proc. Roy. Soc. London, vol. xxviii. p. 218 ; xxx. p. 387 ; xxxi. p. 62. 



14 Ann. dechim., Paris, Ser. 3. tome 1. p. 129 ; Ann. d. Chem., Leipzig, Bd. cxxvii. S. 188. 



