128 PHYSIOLOGICAL CHEMISTRY. 



the potato and the leguminous seeds. The tuber of the potato abounds 

 in starch, but is poor in other nutritive ingredients. 



COMPOSITION OF THE POTATO. 



Starch 20.0 



Albuminous matter 2.5 



Sugar and gum 1.1 



Fatty matter 0.1 



Cellulose 1.0 



Mineral and vegetable salts 1.3 



Water JT4.0 



100. 



The leguminous seeds, on the other hand, contain an abundance of 

 albuminous matter, similar to the caseine of milk, and called " legumine." 



COMPOSITION OF WHITE BEANS. 



Starch . 55.7 



Albuminous matter 25.5 



Fatty matter 2.8 



Cellulose 2.9 



Mineral salts 3.2 



Water 9.9 



100 ."o 



The composition of dried peas is very similar to the above, the 

 starchy matters being present in rather larger, the albuminous in- 

 gredients in rather smaller proportion. Notwithstanding the abun- 

 dance of nitrogenous matter in leguminous seeds, its quality is inferior 

 to that contained in the cereal grains. Peas and beans also have a 

 texture which renders them comparatively difficult of digestion, and 

 requires long boiling to fit them for use as food. The same is true of 

 many juicy and saccharine roots, such as beets and parsnips, which 

 appear to have a comparatively soft consistency, but which neverthe- 

 less need prolonged boiling. The effect of cooking, upon vegetables, is 

 generally to disintegrate and soften their texture, and particularly, by 

 the aid of heat and moisture, to bring their starchy ingredients into a 

 pasty condition. Raw starch is nearly or quite indigestible by man, 

 and if taken into the stomach will often pass unchanged through the 

 bowels ; but when cooked it is transformed into glucose by the diges- 

 tive fluids. It is for this reason that starchy vegetables require more 

 thorough cooking than most kinds of animal food. 



Beside the more solid kinds of vegetable food, many of the pulpy and 

 succulent fruits and herbaceous substances are valuable as an addition 

 to the nutritive regimen celery, lettuce, parsley, spinach, with all the 

 sweet fruits and melons, being used with advantage either in the raw 

 or cooked form. They introduce into the system salts of the vegetable 

 acids, such as malates, tartrates, and citrates, the privation of which 

 for a long time is one of the inducing causes of scurvy. 



It is evident, therefore, that the nutritive value of any article of 



