122 TEXT-BOOK OF PHYSIOLOGY. 



After absorption the iron is utilized in the formation of the coloring-matter 

 of the blood-corpuscles hemoglobin. The organic compounds of iron 

 and the nucleins have been termed hematogens. The amount of iron ingested 

 has been estimated at 10 to 90 milligrams daily, the larger part of which is 

 eliminated in the feces. The relatively small part eliminated by the kidneys 

 and liver is usually taken as the amount metabolized, though it is probable 

 that this is not wholly true, as there is evidence that iron can be retained in 

 the body and utilized again in the formation of new hemoglobin. Contrary 

 to what might be expected, milk contains but a very small quantity of iron 

 not more than 3 or 4 milligrams in 1000 grams (human milk) an amount 

 insufficient for the development of the necessary hemoglobin. This is 

 compensated for, however, by the accumulation of iron in the liver during 

 intrauterine life. According to Bunge, the liver of a newly born rabbit 

 contains as much as 18.2 milligrams per 100 grams of body-weight, while at 

 the end of twenty-four days it contains only 3.2 milligrams per 100 grams of 

 body-weight. 



Vegetable acids increase the secretions of the alimentary canal, and 

 are apt, in large amounts, to produce flatulence and diarrhea. After 

 entering into combination with bases to form salts, they stimulate the 

 action of the kidneys and promote a greater elimination of all the urinary 

 constituents. In some unknown way they influence nutrition; when deprived 

 of these acids, the individual becomes scorbutic. 



Accessory foods coffee, tea, and cocoa when taken in moderation- 

 have a stimulating influence on the nervous system, as shown by the 

 removal of both mental and physical fatigue, by an increased capacity 

 for sustained mental work, and by the persistent wakefulness among those 

 unaccustomed to their use. Coffee more especially increases the frequency 

 and force of the heart-beat, raises the arterial pressure, and hastens the 

 general blood-flow. It has no influence either in the way of increasing or 

 decreasing protein metabolism. 



Tea frequently acts as an astringent on the alimentary canal on account 

 of the tannin which passes into the water when the infusion is made. In- 

 as much as tannin also coagulates peptones, the excessive use of tea as a 

 beverage is apt to derange the digestive organs and the general process of 

 digestion. 



Cocoa is more nutritive than either coffee or tea, on account of the 

 large amount of fat and protein it contains. It is, however, less stimulating. 



The active principles in coffee, tea, and cocoa, and to which their effects 

 are to be attributed, are caffein, thein, and theobromin respectively. These 

 alkaloids are chemically closely related one to the other and to the compound 

 xanthin. They are present in the coffee seeds, the tea leaves, and the cocoa 

 bean to the extent of 1.7 per cent., 1.4 per cent., and 1.6 per cent, respectively. 

 When prepared as a beverage, however, there is three times as much caffein 

 in coffee as thein in tea. 



Alcohol when taken in small quantities stimulates the digestive glands 

 to increased activity and thus promotes digestive power. Its absorption into 

 the blood is followed by increased action of the heart, dilatation of the cutane- 

 ous blood-vessels, a sensation of warmth, and an excitation of the brain. 

 In large quantities it acts as a paralyzant, depressing more especially the 



