PECTIC BODIES 145 



Related to the gums and mucilages are the substances 

 known as galactosanes occurring in the seeds of Leguminosae 

 (Lupinus, Medicago, etc.) ; wood gum or xylane, occurring in 

 wood, etc. etc. These substances have already been mentioned 

 in connexion with the sugars which they give rise to on 

 hydrolysis. 



PECTIC BODIES. 



Many succulent fruits, such as pears, apples, gooseberries, 

 and currants, and also fleshy roots, such as carrots, beetroots, 

 etc., contain, together with the cellulose in the cell walls of 

 parenchymatous elements, a substance which is soluble in 

 water, but whose aqueous solution gelatinizes spontaneously 

 on cooling ; * this substance, which is probably the cause of 

 concentrated aqueous extracts of fruit gelatinizing, is known 

 as pectin. 



According to Fremy,f the hardness of unripe fruit is due 

 to the presence of pectose, an insoluble substance, which is 

 deposited in the cell walls ; as the fruit ripens the pectose 

 undergoes a variety of changes, and is ultimately converted 

 into pectin, the soluble substance capable of gelatinizing. 



According to Schryver and Haynes,! on the other hand, 

 pectin has its origin in pectinogen, a water soluble substance 

 which may be extracted from fruit with 0-5 per cent am- 

 monium oxalate. An alkaline solution of pectinogen at or- 

 dinary temperatures is converted into pectin, which has acid 

 characters, and is precipitated by acids from its alkaline solu- 

 tion as a gel insoluble in water. 



Under the action of an enzyme pectase contained in the 

 plant, pectin is coagulated ; this change was first studied by 

 Fremy, and later by Bourquelot and Herissey ; according to 

 Duclauxll and others, the coagulation is dependent on the 

 presence of calcium salts, and will take place even in the 

 absence of the enzyme. 



*MacNair: "J. Phys. Chem.," 1916, 20, 633. 



f Frmy : " J. Pharm. et Chim.," 1840, 26, 368. 



J Schryver and Haynes : " Biochem. Journ.," 1916, 10, 539. 



Bourquelot and Herissey: " J. Pharm. et Chim.," 1898, [6], 8, 145 ; 1899, 

 [6], 9, 563, and 10, 5. Also Verdon : " J. Pharm. Chem.." 1912, 5, 347. 



|| Duclaux : " Traite" de Microbiologie," 1899, n, 336, and Goyaud : " Compt 

 rend.," 1902, 135, 537. 



IO 



