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INTRODUCTION 



Pathology (t6 7rd6'os, suffering; 6 x670s, science) may he defined 

 as the natural history of diseases, or as the scientiHc study 

 of diseases. The terms "disease," "disordered" and "morbid" are 

 employed to indicate the existence of disturbances of the physio- 

 logical activity of the organs; that is, the presence of some devia- 

 tion from the anatomical and chemical relations of the body- 

 constituents which exceeds the limits of physiological variation and 

 which calls forth such disturbances. 



In ordinary life we designate as "health" a state of the body in 

 which the vital manifestations (nutrition, metabolism, motility, sen- 

 sation, psychical activity) are carried on in harmony; and it is as- 

 sumed in addition that the various organs are of normal structure, 

 and that the individual experiences a feeling of well-being. On 

 the other hand the term "disease" carries with it a conception 

 opposed to this so-called health, that of an irregularity of function 

 and of impairment of efficiency of the organs and systems of 

 organs, accompanied as a rule by a feeling of discomfort. 



The distinctions between these two conceptions merge, however, 

 and are lost when we consider the infinite gradations between health 

 and disease, and as we are required to employ the terms, either 

 empirically or scientifically, in a narrower or broader sense. There 

 might exist, for example, an organ of distinctly faulty structure in 

 an individual without causing any appreciable disturbance of the 

 general health, as a malformed kidney, or a curvature of the spine. 

 One of two paired organs, as a lobe of the thyroid or one of the 

 kidneys, may be anatomically so altered and incapable o£. function 

 as to merit being considered diseased ; nevertheless the individual 

 may feel well and live many years. Moreover in healthy bodies 

 there mav now and again be evinced deviations from the normal 

 vital manifestations which may simulate morbid disturbances, but 

 which are not felt or regarded as such because of their brief dura- 

 tion, because they are soon corrected by the protective and regu- 

 lating mechanism of the body, or are at most expressions of such 



