124 PRINCIPLES OF PHYSIOLOGY 



of hydraulics. We might imitate it roughly 

 by elastic tubes and a force pump. We can 

 drive water through the streets and houses 

 of a town by a head of water or a powerful 

 engine, but even with our present technical 

 skill, we could not automatically regulate the 

 supply according to the wants of different 

 districts by using automatically working 

 elastic and contractile pipes. 



