166 AZOTISED VEGETABLE PBODUCTS. 



cellular plants it is" absent, and the object of many horticultural 

 operations, as blanching, is to prevent its formation. Beet-root and 

 ■white turnips contain only 3 per cent. Lignin is not coloured by 

 iodine. 



All these organic substances, consisting of carbon united with'the 

 elements of water, are easily convertible into each other by the action 

 of sulphuric acid and heat. Similar changes are induced during the 

 growth and development of plants, as will be noticed under the head 

 of flowering, fruiting, and germination. In many unazotised matters 

 the proportion of elements is the same, that is, they are isomeric. 

 Thus, cellulose and starch have the same composition (0^ Hj,, 0^), and 

 are said to be isomeric. The difference in their qualities seems to depend 

 on the mode in which the atoms which make up the molecule are 

 grouped. The form is altered by a re-arrangement of the component 

 atoms. The unazotised products which have been noticed supply 

 materials for the respiration of man and animals, and probably assist 

 in the formation of fat. It is impossible to notice all the compounds 

 of carbon, oxygen, and hydrogen, found in plants. For example, 

 Salicin, Cjg Hjg 0^, a bitter neutral crystalline substance, is procured 

 from the bark of Salix alba. Helix, purpurea, viminalis, pentandra, etc. ; 

 and Phlorizin, C^j H^^ Oj,,, an analogous substance, occurs in the bark 

 of the roots of the apple, pear, cherry, and plum. 



AzoTiSED Peoducts. — There are certain azotised products which 

 exist in greater or less quantity in plants, and which are particularly 

 abundant in grains and seeds. The nutritive matter of wheat consists 

 of starch or unazotised matter, separable by washing, and of azotised 

 matter or glutin. Glutin is composed of certain protein compounds 

 (fibrin, casein, albumin, emulsin), containing carbon, oxygen, hy- 

 drogen, and nitrogen, with some phosphorus and sulphur. Vegetable 

 fibrin is the essential part of the glutin of wheat, and of the cereal 

 grains. It may be procured by treating with ether the glutinous mass 

 left after kneading wheat flour in linen bags under water. Vegetable 

 casein or legwmin is an essential part of the seeds of Leguminous 

 plants, and also of oily seeds. It may be procured in solution from 

 kidney beans and peas, by bruising them in a mortar with cold water, 

 and straining. Vegetable albumin occurs in a soluble form associated 

 with casein. It forms a small proportion of cereal grains. Wheat is 

 said to contain f to 1| per cent ; Eye, 2 to 3f per cent ; Barley, -}^ 

 to ^ per cent ; and Oats, i to J per cent. It is distinguished by 

 coagulating at a temperature of 140° to 160°, and by not being pre- 

 cipitated by acetic acid. Emulsin, or synaptase, has never been 

 obtained in a state of purity. It is a nitrogenous compound, found 

 in certain oily seeds, as in almonds. It exists in the milky emulsion 

 which these seeds form in water, and it is coagulated by acetic acid, 

 and by heat. In bitter almonds it is associated ' with a substance 



