i EXCHANGE OF MATERIAL 39 



reference to the effect of meat extract that "we know nothing 

 about it except that its taste and smell render it palatable to 

 every one. This in itself would entitle it to rank as the best 

 condiment for dishes ; another reason being that it is never 

 taken to excess." 



Other pleasant beverages which are rarely abused are tea and 

 coffee. Like meat broth, they clearly have a stimulating effect 

 on the nervous system and also on the muscular system. They 

 contain caffein and thein, which are chemically closely related 

 to xanthine, a catabolic product of the tissues containing nitrogen. 

 The chemical composition of caffein places it among the trime- 

 thylxanthines. It is mostly decomposed by the tissues ; only in 

 cases where very large quantities are taken (50 centigrms.) does 

 a part appear in the urine in a non- decomposed state. It has no 

 noticeable effect on metabolism ; Voit found that the nitrogen in 

 the urine neither increased nor decreased. In addition to the 

 alkaloid, tea and coffee contain aromatic substances and ethereal 

 oils ; this fact explains their general effect on taste and their 

 somewhat different actions as stimulants. Tea further contains 

 3'03 per cent of salts, salts of iron, sodium, and manganese ; 

 coffee, on the other hand, contains more salts of potassium. 



The seeds of the cocoa plant, from which chocolate is made, 

 contain theobromine, which is a dimethylxanthine. Cocoa is not 

 merely a pleasing beverage, but also a real food, containing about 

 50 per cent of fat and 12 per cent of albumen. There is^no 

 substance which contains a larger amount of nourishment in such 

 a small volume and weight. It is, therefore, a most convenient 

 form of provision for journeys, marches, and rapid military 

 movements. 



Spices, such as pepper, cinnamon, cloves, nutmeg, ginger, and 

 mustard, are condiments pure and simple, having no direct effect 

 on the exchange of material ; they are, however, pleasing to both 

 taste and smell, and stimulate through the nervous system the 

 secretions of the organs both of vegetative and animal life. Their 

 abuse is harmful, but when taken in small quantities they are 

 useful. 



The use of tobacco, which is so common, produces an effect 

 much like that of spices, but may very easily be abused. Clinical 

 and anatomical - pathological experience show that chronic 

 nicotine poisoning favours the development of arterio-sclerosis, 

 catarrh of the pharynx, arrhythmia of the heart, and attacks of 

 angina pectoris. 



The scents of flowers and of certain animal secretions and 

 perfumes in general excite the olfactory sense and stimulate 

 nervous and psychical activity. 



As a general rule, it may be said that condiments, spices, and 

 scents are no less necessary to man than the true foods, which in 



