lO FIRST PRINCIPLES OF CONFORMATION. 



heptane, which is the chief constituent of paraffin oil, is a combination 

 of 7 atoms of carbon (C) and i6 atoms of hydrogen (H), both of 

 which elements have a strong affinity for oxygen. When the oil is 

 ignited, its carbon and hydrogen unite with the oxygen of the air, 

 as we may see by the following equation : — 



C, Hie + II Oo = 7 C Oo + 8 Ho O. 



(Heptane) (Oxygen) (Carbonic acid gas) (Water) 



This conversion of chemical ai^nity into heat is somewhat similar 

 to that which we see when a heavy stone falls on hard ground from 

 a high cliff, in which case, gravitation (the attraction which all 

 bodies in the universe have for each other) is converted into move- 

 ment ; and movement into heat, as we can feel by placing our hand 

 on the spot that has been struck. Unlike gravitation, chemical 

 attraction can act only when bodies (molecules or atoms) which have 

 this affinity for each other, are very close together. 



After the latent energy in the fuel of a steam engine has been 

 changed into heat, the heat that has been transmitted into the 

 boiler becomes converted into another form of force (repulsion), which 

 causes the particles of the confined steam to recede from each other, 

 and consequently to exert pressure on the piston ; and finally this 

 pressure becomes changed into movement. As some of the con- 

 stituents of coal are already oxidised, and as it contains a certain 

 proportion of mineral matter, it is not such a potent force-producer 

 as paraffin oil. 



In horses, as in men, the fuel for the maintenance of heat and 

 movement is obtained from that portion of the food which has been 

 assimilated (taken up by the system), and is distributed in varying 

 proportions throughout the body. There are many kinds of this 

 animal fuel, all of which, in order to be effective, must contain 

 elements that have an affinity for oxygen and that have not yet 

 been oxidised. For instance, glycogen (Cg H.^ O^), which is un- 

 doubtedly a valuably form of fuel in the animal economy, and 

 which is formed in the liver, contains five parts of water and six 

 parts of carbon. The fuel is conveyed in a dissolved state to the 

 various tissues by the arterial blood, which is pumped to its many 

 destinations by the heart. The lungs obtain oxygen from the 

 breathed-in air and supply it to the blood, which carries it to the 

 tissues along with the fuel. The waste products (carbonic acid, 

 urea, surplus water, etc.) are removed from the system, chiefly by 

 means of the lungs, skin, heart, kidneys, and intestinal organs. 



From the foregoing considerations^ we can see that 

 the conformation of a stayer must be such as will afford 



