NORMAL HISTOLOGY. 



INTRODUCTION. 



During life all parts of the human body are the seat of constant 

 activity. This is a fact too readily overlooked by the student who 

 gains his knowledge of the structures of the body by a study of the 

 tissues after death. To make that study of use to him in his medi- 

 cal thinking he should constantly bear in mind that he is viewing 

 the mechanism of the body while it is at rest, and, furthermore, 

 that the methods employed in the study of the minute structure of 

 the parts not only arrest the normal activities of those parts, but 

 expose them to mutilation. He must, therefore, constantly supple- 

 ment the knowledge of structure he gains by his histological studies 

 by recalling to mind and applying that which he has acquired by 

 a study of physiology, habitually associating his ideas of structure 

 and functional activity, until he can hardly think of what a struct- 

 ure is without at once recalling what it does. This he cannot do 

 till he has mastered at least the general outlines of systematic 

 anatomy and of physiology. Those two fundamental subjects are 

 brought together by an intelligent study of the minute structure of 

 the body, histology, which, for this reason, has also and appro- 

 priately been called physiological anatomy. 



But the student of medicine must go beyond this. To the con- 

 ception of the body during health, which he has formed by this 

 thoughtful method, he must then add a conception of the influence 

 exerted, both on the structure and activities of the body, by ab- 

 normal conditions which disturb or thwart the usual working of 

 that complex mechanism. The more closely he can make those 

 conceptions agree with observed facts, the more perfect will become 

 his ability to interpret the physical signs and symptoms of disease, 



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