A POSTAL SYSTEM 221 



In the human body the time gearing is so different from 

 that of a motor cycle that, if we are to make its nature 

 clear, we must study it in a machine, not made of metal, 

 but made of men — an army. An army is a fighting 

 moving machine composed of hundreds of thousands or 

 millions of living units. We have seen that the human 

 machine is made up of countless millions of living units 

 — the individual soldiers of our bodies. An army, like 

 the human body, is made up of several systems or depart- 

 ments. The fighting units are formed into army corps, 

 divisions, brigades, battalions, companies, and platoons. 

 An army has its service corps or alimentary system, its 

 transport and its intelligence services. The brain of the 

 army is placed in a controlling centre — General Head- 

 quarters. That centre has to be linked up with all 

 departments so that the work done by each may be timed 

 and co-ordinated to serve a common purpose. The staff 

 at general headquarters has many contrivances at its dis- 

 posal for issuing orders to and of obtaining information 

 from the various departments spread out between the 

 firing-line and the base. It may use the ancient and 

 primitive method of dispatching orders by messengers, 

 or, if time is not pressing, send them through the army 

 postal system. If orders are urgent, then a totally differ- 

 ent contrivance is employed ; they are dispatched over 

 the wires or nerves which link general headquarters to 

 every part of the fighting machine. The activities of 

 millions of soldiers are thus co-ordinated by the em- 

 ployment of various systems of communication. It is 

 also manifest that neighbouring army corps, divisions, 

 brigades, battalions, and companies must be kept in touch 

 with each other's movements. They cannot trouble 

 higher quarters with each disposition which has to be 

 made to keep the firing-line intact. There must be in- 

 tercommunication independent of headquarters. Each 

 soldier, although acting under strict orders, still retains 

 individuality of action. He may communicate with and 

 influence the men who are fighting side by side with him. 

 There is also direct communication between the units in 



