THE GENERAL NATURE OF DIET 161 



One effect of this stimulation of the nerves is seen probably in its slight 

 laxative action on many, especially " nervous" persons. The peristalsis 

 of the gut is hastened, a result of the use of coffee which may, however, 

 be due to the volatile oils etc., called collectively coffeol, rather than to the 

 alkaloid caffeine. 



That the brain is more or less functionally altered by coffee may be 

 noted in the pain in the head which many persons experience when they 

 omit for once their usual coffee at breakfast. A nervous restlessness and 

 tremulousness follows the taking of two much coffee, the excitement of 

 the nervous system having then gone beyond its normal intensity. That 

 coffee increases metabolism is proved by the increased excretion of urea 

 and of carbon dioxide during its use. "W ood calls attention to the fact that 

 coffee stimulates both the intellect and the imagination, while opium, 

 another brain-stimulant under some conditions, acts largely to increase 

 the latter and not the former. Caffeine in large doses has a distinctly 

 diuretic action, increasing the urea to be excreted. As we saw above, 

 caffeine is a xanthin, and it is now known that the nuclei of cells contain 

 xanthin-like bodies. It is supposable, therefore, that coffee may actually 

 feed the nerve-cells of the brain as well as stimulate them. Its action on 

 the heart is to augment its force and frequency, but the effects on the 

 blood-pressure are too complicated in various conditions to be stated here. 

 Children are especially susceptible to the action of caffeine and hence to 

 tea and coffee, the cerebral stimulation being evinced in them often by 

 night-terrors and other harmful causes of insomnia. Over-use of 

 coffee in adults leads sometimes to a depressive neurasthenia, which 

 disappears when the occasioning substance is withdrawn. Its tendency 

 to cause indigestion by checking hydrolysis is known to all a slight 

 attack of dyspepsia accompanied by unpleasant sensations in the head 

 altogether known commonly as a "biliousness." These are the chief 

 of the bad results accompanying the excessive use of the beverage, the 

 proper amount for benefit having to be determined by every individual 

 for himself. It must not be forgotten that the beverage coffee is usually 

 accompanied by milk or cream and sugar, both of which are of course 

 highly nutritious substances. The last of these, sugar, in particular is 

 a supporter of muscular action and a banisher of muscular fatigue. 

 Thus, in practice, for the great majority of cases, coffee as used is a 

 distinct addition to a meal aside from its mentally stimulating action. 

 Where there is a tendency to indigestion both of these additions to the 

 decoction of the coffee-bean are apt to be harmful, the sugar because it is 

 liable to ferment before its absorption as dextrose. The harmfulness 

 of the milk is more obscure, but it is believed to be due to the formation 

 of a chemical union between the alkaloid and the proteid casein ogen, 

 the product of which for many individuals is very indigestible. Thus, 

 black coffee is often less objectionable and more useful than when taken 

 with cream and sugar. 



Tea, as has been learned from our statements about caffeine, is much 

 like coffee in its physiological action and effects, but, weight for weight, 

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