DIGESTION. 7 



in the digestive liquids. Fruits and succulent vegetables 

 owe their nutritive value to the sugar and to the organic 

 acids and the salts which they contain. Their percentage 

 of albuminous material is very small. 



Inorganic Salts of Food. Beef yields, when dry, about 

 4 per cent, of ash, potash constituting more than two-thirds 

 of the total bases. The most important potassium salts are 

 phosphate and chloride. The proportion of sodium salts 

 is very small. In boiling meat, nearly the whole of its 

 alkaline salts pass into the bouillon. Wheat flour contains 

 about 2 per cent, of ash, of which one-third is reckoned as 

 potash and nearly half as phosphoric anhydride. The 

 constitution of the ash of potatoes and other juicy vege- 

 tables is similar, but the yield of phosphoric acid is relatively 

 less ; the percentage of potash is about four times as great 

 as that of all the other bases together. Milk yields about 

 2*5 per thousand of ash, of which about I per thousand 

 is reckoned as potash, 0*25 as soda, and about o'4 as lime. 



In an adequate diet comprising 250 grammes of meat, 

 and 400 grammes of bread, the former would yield 1*5 

 gramme of potash, the latter r6. An adequate diet of 

 milk (two and a half litres) would yield about 3 grammes. 



DIGESTION, 



including the Physiology of the Liver and Pancreas. 



Human saliva, the mixed secretion of the submaxillary, 

 parotid, and sublingual glands, and of the mucous glands 

 of the mouth, is a tenacious, slightly turbid, and slightly 

 alkaline liquid ; it contains about half per cent, of solids, 

 of which about half is inorganic. The organic constituents 

 are albumin, globulin, mucin, and a diastatic ferment ; the 

 salts are those of the blood, but the proportion of earthy 

 bases is larger. Ferric salts colour saliva blood-red : this 

 reaction is due to sulphocyanate of potassium, which it 



