XI INSTRUCTION IN PHYSIOLOGY 297 



and how to influence them towards the main- 

 tenance of health and the prolongation of life; 

 the business of the general public is to give an 

 intelligent assent, and a ready obedience based 

 upon that assent, to the rules laid down for their 

 guidance by such experts. But an intelligent 

 assent is an assent based upon knowledge, and the 

 knowledge which is here in question means an 

 acquaintance with the elements of physiology. 



It is not difficult to acquire such knowledge. 

 What is true, to a certain extent, of all the physical 

 sciences, is eminently characteristic of physiology 

 the difficulty of the subject begins beyond the 

 stage of elementary knowledge, and increases with 

 every stage of progress. While the most highly 

 trained and the best furnished intellect may find 

 all its resources insufficient, when it strives to 

 reach the heights and penetrate into the depths 

 of the problems of physiology, the elementary 

 and fundamental truths can be made clear to a 

 child. 



No one can have any difficulty in comprehend- 

 ing the mechanism of circulation or respiration ; 

 or the general mode of operation of the organ of 

 vision ; though the unravelling of all the minutiae 

 of these processes, may, for the present, baffle the 

 conjoined attacks of the most accomplished physi- 

 cists, chemists, and mathematicians. To know 

 the anatomy of the human body, with even an 

 approximation to thoroughness, is the work of a 



