6 
4. Extractives (many substances of divers nature that occur 
in minute proportions, such as pigments, and vas as a hetero- 
eneous group, are conveniently designated in this w: 
5. Organic acids and their salts (malic acid, citric eer potas- 
sium tartrate, e 
6. Mineral pee i. é., salines (chlorids, phosphates, etc.) 
7. Enzymes (substances that induce important chemical 
changes during the life and after the death of the vegetable forms 
containing them). 
‘ases (oxygen, carbon dioxid, etc.). 
9. Water—usually the most abundant constituent. 
Of these types of substances, the extractives (4), organic acids 
and their salts (5), mineral salts, 1. e., salins (6), and water (9), 
are easily absorbed (without essential molecular changes) from 
the pase: tract—their molecular simplicity, diffusibility 
and comparative non-toxicity give them ready access, Lata 
feu aa absorbing channels, to the blood. The ¢ es (7) 
and gases (8) are present in very minute quantities tn ak 
foods and add nothing of consequence to the nutritive value of 
such foo 
The digestible substances in vegetable foods, the carbohydrates 
. lipins (2), and proteins (3), are characterized, for the most part, 
eee co ace colloidal perversity and comparative 
non-diffusibili There are exceptional substances in these 
three “pace ce as cane-sugar, which, though comparatively 
simple molecularly, non-colloidal in character and_ readily 
diffusible, are nevertheless chemically unsuited for direct assimi- 
lation—they don’t seem to fit in the body anywhere! As in the 
case of the rest of the members of these groups, however, digestion 
changes these substances into products that are directly absorb- 
able and readily assimilable. The representatives, in vegetable 
foods, of these three groups of nutrients are like large rock-masses 
direct from the quarry—unsuitable in form and size for construct- 
The carbohydrates, lipins and proteins in vegetable foods are 
‘‘cut and shaped” by the digestive processes into construction 
units of small molecular size, which are non-colloidal in character, 
