INTERNAL-COMBUSTION ENGINES 35 



by looking at the drawings given in fig. 5.. There the 

 fibres are drawn as if they were 10 millimetres wide (f of 

 an inch), but that is one hundred times wider than they 

 actually are. If we were to enlarge a man who is 6 feet 

 tall on the same scale we should have to make him 600 

 feet high ! But although these cylinders are so narrow 

 that they cannot be seen with the naked eye except when 

 there is a mass of them joined together forming a thread or 

 fibre, yet they may be 10 millimetres long or even 25 milli- 

 metres, which is equal to an inch. They lie side by side 



Muscle cylinder 

 (ElonqaUJ) End plate Werve fibre 



Muscle cylinder 

 (Contracted ) 



Fig. 5. — A, above, a primitive muscle fibre or cylinder in an uncontracted state ; 

 below, a nerve fibre is seen going to it and ending on a nerve plate. B, a 

 cylinder in a state of contraction with its nerve fibre. 



in rows, and are joined together end to end like a string 

 of sausages. At one end of the muscle the cylinders are 

 joined to tough white fibres which fix the muscle to the 

 bone from which it exerts its power. At the other end 

 of the muscle the cylinders are joined to strong white 

 fibres which become collected together and form the 

 piston cord or tendon of the muscle. All the cylinders 

 thus work on one piston. 



Thus in a muscle like the biceps we have an engine 

 made up of tens of thousands of microscopic cylinders, 

 with combustion chambers which are so minute that the 

 most powerful microscope has never revealed them, yet 

 we know that they must exist for combustion certainly 



