126 APPLIED PHYSIOLOGY 



and cold countries. When carefully prepared, canned food is as whole- 

 some as food recently cooked. When opened it soon spoils. 



197. Scurvy. When men have been living for months 

 upon bread and salt meat, without fresh food, there some- 

 times comes a disease called scurvy. Th6 gums become 

 sore, and the legs ache and turn "black and blue" as 

 though they were bruised. Then fruit or green vegeta- 

 bles are of the highest value, probably because they fur- 

 nish a good supply of nucleo-albumin, in which old bread 

 and salt meat are apt to be deficient. 



198. Seasonings. Pepper, mustard, nutmegs, cloves, and all such 

 sharp-tasting things are added to food simply for their taste. They are 

 probably neither digested nor oxidized, and yield neither weight, nor 

 heat, nor energy. They irritate and burn the stomach just as they do 

 the mouth. Yet their pleasant taste may be of value in promoting the 

 flow of the digestive juices. 



199. Tea and coffee. Tea and coffee are often sup- 

 posed to supply food to the body. They belong to the 

 class of substances which, acting through the nervous 

 system, spur on the work of the cells of the body, espe- 

 cially of the brain. They supply no heat or energy for 

 the extra exertion. Substances which excite the cells to 

 action, without giving them material out of which to 

 develop heat and energy, are stimulants. The active 

 principle of tea and coffee is a stimulating substance 

 called caffeine which spurs the cells of the body to do 

 more work. They enable a person to do a larger amount 

 of work in an emergency, and when the body is tired they 

 rouse the digestive and assimilative organs to renewed 

 activity, so that these quickly prepare a new supply of 

 food. When they are used continually the body learns to 

 rely upon their stimulation. Thus a habit of drinking them 

 is formed which is not easily broken. 



