20 HUMAN PHYSIOLOGY 



cause of the scurvy outbreak, but the lack of potash 

 in the meat. When proper food is supplied contain- 

 ing potash, scurvy disappears. Vegetables contain 

 potash, as also do fresh meats and potatoes; and the 

 remarkable fact was noticed that in Irish famines 

 where the sufferers had little else than potatoes to 

 eat, though the people were starving and emaciated, 

 no scurvy appeared. Minerals thus enter intimately 

 into the compositon of the body, and are demanded 

 as an essential part of our diet. 



THE ENERGY-PRODUCERS. The energy-producing 

 foods are fats, starches, and sugars. Fats stand 

 out distinctively as heat-producing foods, but it is to 

 be noted that a food which is capable of producing 

 heat is also capable of developing energy or working- 

 power. Probably the starches and sugars are more 

 effective as energy-producers than fat, because they 

 are specially supplied to the muscles; but the typical 

 diet must include a supply of both items, greater 

 working power being developed from the combina- 

 tion of fats, starches, and sugars, than from the 

 taking of one of these foods only. Fat is an 

 extremely important item in our diet. It is not 

 merely required as part of our bodily substance, 

 being formed out of starch and sugar chiefly, but 

 likewise seems to play an important part in assisting 

 the digestion of other foods, whilst it is especially 

 the food of the nervous system. Starch and sugar 

 are derived from the vegetable world, which may 

 also yield us forms of fatty food in the shape of oils. 

 These two classes of foods, starches and sugars on 

 the one hand, and fat on the other, are closely 

 related in chemical composition. It is curious to 

 note that the body possesses the power of convert- 

 ing starchy foods into fat. This is well seen in the 



