INTRODUCTION. 67 



little understood transmission of physiological impulses from cell to cell. 

 Whether this is by protoplasmic continuity or in some other way, we do 

 not know. But it should not be left out of the account in some of the 

 more complex and subtle problems which, in health as in disease, the 

 life of the cell and the life of the body present. 



When we study the so-called causes of disease, we should remember 

 always that underlying the manifestations of disease, as well as sustain- 

 ing the correlated processes which we name health, are the complex and 

 ceaseless chemical transformations which in both health and disease 

 alike supply the energy which sustains all expression of life. So that 

 what we are wont to call the causes, whether external or internal, of dis- 

 ease are really not primary causes, but liberating impulses or excitants 

 which sway and modify the orderly transformations of energy constitut- 

 ing health with those manifestations of perturbed function or altered 

 structure, or both, on which our conceptions of disease are framed. 



Pathology, then, deals with the disturbances of function and the al- 

 terations in structure in living beings, induced by unusual agencies and 

 conditions. The functional disturbances thus induced are embraced as 

 symptoms of disease in pathological physiology, which so largely dominates 

 the scientific activities of the physician, and forms the basis for the prac- 

 tice of his art. The phenomena of pathological physiology are in no 

 sense opposed to those of normal physiology, but are their inevitable 

 correlatives when the living body is placed under sufficiently abnormal 

 conditions. Pathological morphology is concerned with the structural al- 

 terations of the organism which may result from abnormal conditions. 

 Pathological morphology deals with both the gross and the microscopic 

 alterations of structure, and hence embraces both pathological anatomy 

 and pathological histology. 



But alterations in structure are so closely associated with disturbances 

 in function, and both are so constantly dependent upon the inciting fac- 

 tors in disease, that an intelligent study of morphology necessitates a 

 constant consideration of etiology and of certain phases of pathological 

 physiology. 



It is customary and convenient in the study of pathology to consider 

 together the general or elementary abnormal processes and conditions 

 and the etiological factors in disease without reference to their special 

 manifestations in particular organs or parts of the body. This division 

 of the subject is called General Pathology. Special Pathology deals with 

 the forms and details of lesions in individual organs or parts of the 

 body. 



The human body is so complex in its organization that the student of 

 pathology, like the student of normal morphology and physiology, is 

 under the constant necessity of seeking light through the study of sim- 

 pler organisms. In our extremely differentiated and intimately co-ordi- 

 nated cells, many features fundamentally simple are veiled or modified ; 

 so that we can understand them only when we interpret them in the 

 light of less advanced forms. 



