No, 7. DEPARTMENT OF AGRICULTURE. 603 



sufficient to say that protein is like the white of an egg or washed 

 lean meat. It contains the element of nitrogen and it makes up 

 the working machinery or the structural part of the body. Then, 

 in addition to that we have more or less fat in the body, which 

 is not essential to the working of the body, but constitutes a re- 

 serve of force or energy. The food that has been given to the 

 animal in excess of its immediate needs has been burned into fat. 

 Of course there are other things in the animal body, but these 

 two are the essential ones, the protein making up the working mach- 

 iner}', and the fat, which may be called reserve food. 



Now, there is a pretty close analogy between the body of an 

 animal and a gasoline or steam engine. They are not exactly alike, 

 of course, but in one respect they are very similar. They are both 

 machines for the conversion of chemical energy work. In the 

 steam engine, for example, we burn coal under the boiler, and by 

 various devices we convert the resulting heat into work, which 

 we apply for our own purposes. In case of the gas, alcohol or 

 gasoline engine, the transformation is more direct. The fuel is 

 burned in the cylinder of the engine and its energy coverted in this 

 way into the motion of the piston and so into work. In much the 

 same way the animal burns fuel and produces work. The fuel is 

 its food — corn, for instance. I remember that several years ago 

 the farmers in the Middle West were burning corn for fuel, because 

 the price was so low that they could not afford to haul it to the 

 station. Thej^ might have also burned the corn under the boiler 

 of an engine and so used it as a source of energy for the performance 

 of work. Now, when we feed corn to the animal, that corn is 

 burned, just as truly ais fuel is burned under a boiler and we can 

 utilize its energy in the shape of work done by the animal. More- 

 over, if we do not utilize it all in this way the animal will store 

 the surplus in the shape of fat and meat against some future time 

 of need. Then, when we slaughter the animal and eat the meat, 

 we are using this stored up fuel to drive our own bodily machinery. 

 We, ourselves, cannot eat hay, or bran, or cottonseed meal, but 

 we have converted them into beef or pork, or mutton or milk, which 

 we use as a source of energy to our own organization. 



Now, if we are running a gasoline engine on our farms to do our 

 work, we must have iron and brass, and babbit metal and similar 

 materials to keep that engine in repair. The same thing, exactly 

 is true of the body of the animal. It wears out constantly, and must 

 have repair material continually. Now, as I have pointed out, the 

 chief constituent of the body is protein, and to repair it we must 

 have protein. We can no more keep it in repair by giving it starch 

 or sugar or fat than we can keep a gasoline engine in repair by 

 giving it more gasoline. These things furnish fuel, but they cannot 

 be used to make repairs. It seems that almost anything the animal 

 can digest can be converted into fuel, but to build up and repair 

 we must have protein material. 



As you know, I have been interested in the last few years in 

 studying some matters relating to the su])i)ly of energy to the body, 

 but i propose to speak to you this morning of the necessary supply 

 of protein material to the body. 



We are accustomed to speak of a balanced ration as one which 

 contains protein and fuel material in due proportions, and we make 

 calculations showing what the nutritive ratio should be, I think it 



