264 THE ENGINES OF THE HUMAN BODY 



of living human units and make up the nations which 

 lead in the van of civilisation. We can get light on 

 the nervous organisation of our bodies if we look for 

 a moment at the manner in which the nerve system 

 of a nation has been evolved. Time was, and that not 

 many centuries ago, when a man had to supply all his 

 personal wants : he had to be farmer, fisher, hunter, 

 tailor, shoemaker, carpenter, blacksmith, builder, warrior, 

 and surgeon. The chieftain regulated the small tribal 

 machines of which the primitive individuals formed 

 loosely knitted parts. Then came the modern period 

 of specialisation, and the work formerly done by one 

 individual was parcelled amongst a thousand specialists 

 or more. In this evolutionary movement a great group 

 of individuals or units became set aside or specialised 

 to serve as a brain or government for the national machine 

 — to receive information from all its parts, and to issue 

 orders to all. The brain came to have at its disposal 

 certain executive departments — a navy, an army, judges, 

 magistrates, and police. Now Nature in building up the 

 human machine has pursued a course not unlike that 

 which has led to the evolution of a modern national 

 machine. In her primitive animate designs the living 

 units were self-supporting ; each could procure and 

 assimilate its own fuel ; it looked after its own supply 

 of oxygen ; it carried out its own movements ; it kept 

 up its own circulation ; it could dispatch a message from 

 one part of its minute body to another part. Then came 

 evolutionary specialisation and the welding of all the 

 differentiated units into a machine. Some became fuel 

 attendants ; others took a hand in pumping the blood, 

 or helped in its ventilation, or joined the police or 

 sanitary services of the body machine. Then in one 

 group of units the power to contract, which was inherent 

 to a slight degree in the primitive type, became their 

 special prerogative ; they were converted into muscle 

 spindles -or cylinders. But the group which interests 

 us most here is that which was set aside to form a 

 nervous or governing service. The primitive animate 



