OUR BONES ARE LIVING LEVERS 51 



the face upwards, but where are the muscles which serve 

 as their opponents or antagonists and reverse the move- 

 ment ? In a previous chapter it has been shown that 

 every muscle has to work against an opponent or 

 antagonist muscle. Here we seem to come across a 

 defect in the human machine, for the greater straight 

 muscles in the front of the neck, which serve as 

 opposing muscles, are not only much smaller but are 

 at a further disadvantage by being yoked to the pre- 

 fulcral end of the lever, very close to the cup on which 

 the head rocks. However, if the greater straight muscles 

 lose power by working on a very short lever, they gain 

 in speed ; we set them quickly and easily into action 

 when we give a nod of recognition. All the strength or 

 power is yoked to the post-fulcral end of the head ; the 

 pre-fulcral end of its lever is poorly guarded. Japanese 

 wrestlers know this fact very well, and seek to gain 

 victory by pressing up the poorly guarded pre-fulcral 

 lever of the head, thus producing a deadly lock at the 

 fulcral joint. Indeed, it will be found that those who use 

 the jiu-jitsu method of fighting have discovered a great 

 deal about the construction and weaknesses of the levers 

 of the human body. 



To merely poise the head on the atlas may seem to you 

 as easy a matter as balancing the beam of a pair of scales 

 on an upright support. I am now going to show that 

 a great number of difficulties had to be overcome before 

 our heads could be safely poised on our necks. The 

 head had to be balanced in such a way that through the 

 pivot or joint on which it rests a safe passageway could be 

 secured for one of the most delicate and most important 

 of all the parts or structures of the human machine. 

 We have never found a good English name for this 

 structure, so we use its clumsy Latin one — Medulla 

 oblongata — or medulla for short. In the medulla are 

 placed offices or centres which regulate the vital 

 operations carried on by the heart and by the lungs. 

 It has also to serve as a passageway for thousands of 

 delicate gossamer-like nerve fibres passing from the brain, 



