A HARD-WORKING DIET. 359 



as a fact and practically acted upon in public dietaries 

 aiid by artizans and navvies, who, without knowing 

 anything of carbon and nitrogen, eat what experience 

 tells them they require. (See Appendix.) 



It is only within the last fifty years, roughly speak- 

 ing, that any attention has been paid to the proportion 

 of carbon, hydrogen and nitrogen in foods, and only 

 quite recently since 1866 that the work they do in 

 the body, and the amounts of them needed for different 

 kinds of work, has been understood. 



It may perhaps seem leaving the immediate subject 

 of " Fish in Diet " to pause to allude to this at all, but 

 it will be seen that unless the values of different foods 

 in general use is understood, the relative value of any 

 particular food, whether beef, mutton, bacon, or fish, 

 cannot be understood. Further than this, there is a 

 wide difference in the values of different kinds of fish. 

 Though it would add much to the interest of under- 

 standing this modern study to go through the history 

 of how it came about, it would take time, and it is not 

 essential to understanding the present views. 



Chemistry cannot explain everything with regard Influence of 



thought on 

 to the connection between food and work. There is digestion. 



that mysterious connection between thought and 

 digestion and digestion and thought. We cannot say 

 give a man so much C and N and he will be able to 

 do so much muscular work. The receipt of depressing 

 news may quite upset his power to eat the food or 

 to digest it, and the C and N must be in the blood 

 before it can be of practical use, so that the mere fact 

 of eating so many ounces of carbon and nitrogen 

 compounds does not necessarily imply the power to 

 do work All that chemistry can do is to show what 



