680 THE POPULAR SCIENCE MONTHLY. 



or any one in this matter ; I only want you to understand distinctly 

 that a person who can not get a full allowance of lean meat, or who 

 does not choose to get it, is not necessarily ill fed for that reason, even 

 though he have to do hard work with his muscles. 



C. If a large amount of nitrogenous food is not wanted as food for 

 muscle or other tissues for plastic purposes, that is to say how is the 

 excess disposed of ? 



M. The part of the nitrogenous food which is not wanted for plastic 

 purposes is, after digestion, resolved by the action of the liver into 

 urea, and the other excrementitious products which are met with in 

 the urine, and into a compound containing carbon, hydrogen, and oxy- 

 gen, without any nitrogen, which compound may he the substance 

 called amyloid substance or glycogen. This non-nitrogenous com- 

 pound is destined to serve as fuel for the production of heat and other 

 forms of force. The portion eliminated as urea, which is simply excre- 

 mentitious, and the complemental portion, which is destined to serve 

 as fuel, is as 3320 to 6G - 80 ; and therefore it is easy to see that a large 

 part of the nitrogenous food but little less than two thirds, that is to 

 say may be devoted to other than plastic purposes, and that a little 

 more than one third may be simply wasted. Moreover, the compara- 

 tively small portion of nitrogenous food which is actually wanted for 

 plastic purposes is, there is reason to believe, eventually disposed of in 

 the same way as the portion which is not used for plastic purposes, a 

 little more than one third being wasted as urea, and a little more than 

 two thirds being utilized as fuel. And if this be so, the question arises 

 whether the fuel into which a large part of the nitrogenous form of 

 food is resolved sooner or later is the best form of fuel for your pur- 

 poses whether, for example, you were wise in picking out the fat 

 and in taking dry toast ? 



C. I leave you to find the answer to this question. 



M. There is, I think, good reason to believe that much of the fuel 

 without which life can not be maintained may be more easily supplied 

 by non-nitrogenous substances than by nitrogenous substances. The 

 fuel in nitrogenous food is not ready-made. This food has to be trans- 

 formed, first of all, into albuminose or peptone, and then this albumi- 

 nose or peptone has to be broken up, partly into the excermentitious 

 portion which passes out of the system by way of the kidneys, and 

 partly into the residual portion which is destined to act as fuel. An 

 abundant supply of gastric and pancreatic and intestinal juices is 

 wanted in order to bring about the proper formation of albuminose ; 

 without a healthy condition of liver and kidney it is evident that the 

 albuminose may not be broken up (this breaking-up occurs chiefly in 

 the liver) into urea and amyloid substance or glycogen, and that the 

 urea (which passes out of the system by way of the kidneys) may not 

 be eliminated. Moreover, it seems to be certain that no one can take 

 a large amount of meat and other highly nitrogenous compounds for 



