88 ON ELEMENTARY INSTRUCTION IN PHYSIOLOGY. [LECT. 



people who yet would vigorously object to give a 

 verbal assent to the doctrine itself. However this 

 may be, the main point is that sufficient knowledge 

 has now been acquired of vital phenomena, to justify 

 the assertion, that the notion, that there is anything 

 exceptional about these phenomena, receives not a 

 particle of support from any known fact. On the 

 contrary, there is a vast and an increasing mass of 

 evidence that birth and death, health and disease, are 

 as much parts of the ordinary stream of events as the 

 rising and setting of the sun, or the changes of the 

 moon ; and that the living body is a mechanism, the 

 proper working of which we term health ; its disturb- 

 ance, disease ; its stoppage, death. The activity of 

 this mechanism is dependent upon many and compli- 

 cated conditions, some of which are hopelessly beyond 

 our control, while others are readily accessible, and 

 are capable of being indefinitely modified by our own 

 actions. The business of the hygienist and of the 

 physician is to know the range of these modifiable 

 conditions, and how to influence them towards the 

 maintenance of health and the prolongation of life ; 

 the business of the general public is to give an intelli- 

 gent 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 



