CUTTING AND COOKING FOOD. 343 



called lignin, or woody fibre, which frequently almost completely 

 fills their interstices ; while, at other times, as in the grains of 

 the cerealia, potatoes and other tubers, the cells contain a quan- 

 tity of small ovoidal globules, varying in size, constituting /ecuZa 

 or starch; and lastly, in the case of the young organs of plants, 

 the cells contain only a more or less viscous fluid, holding in solu- 

 tion mineral salts and various organic substances, the principal of 

 which are gums, gelatinous combinations, designated by the gen- 

 eral name of albuminous substances' We conclude, then, that 

 if heat aids in rendering the nutritive principles of roots and 

 grains more accessible to the assimulating faculty, it will also 

 assist in softening the fibre of hay and straw. The cell walls 

 which imprison the alimentary substances mentioned, will, by the 

 joint processes of cutting and steaming, be more or less broken 

 and weakened. 



" The following extract from Johnston's Agricultural Chemis- 

 try, shows the further effect of heat upon starch itself: 



" 'When wheat flour, potato, or arrowroot starch is spread 

 upon a tray and gradually heated in an oven to a temperature 

 not exceeding 300° F., it slowly changes, acquires a yellow or 

 brownish tint, according to the temperature employed, and be- 

 comes entirely soluble in cold water. It is changed into dextrin 

 gum. * * * During the baking of bread this conversion of 

 starch into gum takes place to a considerable extent. Thus Vogel 

 found that flour which contained no gum, gave, when baked, a 

 bread of which eighteen per cent., or nearly one-fifth of the 

 whole weight, consisted of gum. Thus, one result of baking, is 

 to render the flour starch more soluble, and therefore more easily 

 digested.' Of starch he says: 'It is a property of starch of all 

 kinds, to be insoluble in cold water, but to dissolve readily in 

 boiling water, and to thicken into a jelly, or paste, as it cools.' 

 It is supposed that, by digestion, starch becomes converted into 

 gum or sugar, and the latter probably becomes absorbed. It is 

 also an element of respiration, and, according to Liebig, con- 



