INFECTIOUS 

 AND PARASITIC DISEASES. 



CHAPTER I. 



CAUSES OF DISEASE. 



Since disease is a deviation from that state of the 

 body which is called health, it is appropriate, before 

 taking up the '^causes of disease," to define, briefly, 

 what health and disease are. 



Health may be defined as that condition 

 Health, of the body in which all of its functions are 



normally performed, to the end, that a 

 feeling of mental and bodily comfort is experienced. It 

 is a nice balance, or equilibrium, maintained between 

 our bodies and the surrounding world. Eating, drink- 

 ing, and sleeping, work, play, and rest, are factors that 

 should promote a general feeling of well-being, that 

 in turn manifests itself in the desire and ability to eat, 

 drink, sleep, work, play, and rest, all normal functions 

 which the healthy human being craves. 



Disease, on the other hand, is characterized 

 Disease, by a rupture in the relationship of our 



bodies to our surroundings, which leads 

 to disturbed functions, and to unusual subjective sen- 

 sations and objective phenomena. Whatever breaks 



