PHYSIOLOGIC CHEMISTRY. 21 



No one can be a successful physician who does not understand 

 at least the more important functions of the human body, and the 

 greater the knowledge he possesses of physiology, the broader will 

 be the scientific groundwork on which he has to build. Disease 

 is a departure from the normal or physiologic condition. A dis- 

 eased organ performs its function in an abnormal manner, and to 

 succeed in correcting the diseased condition one must first be able 

 to recognize this abnormal action, which can only be done by 

 knowing how the organ acts in health that is, by understanding 

 its physiology. Even with this knowledge one may be unable to 

 accomplish the desired object, for the structure of the organ may 

 be so changed that no means can be applied which will restore it 

 to its normal condition ; but one is certainly more likely to succeed 

 if possessed of a knowledge of its physiology than if ignorant of it. 

 The study of human physiology is but the study of the human 

 functions, and when these functions are thoroughly understood 

 the science is mastered. 



Classification of Functions. The functions of the body 

 may be classified as follows : 1. Nutritive Functions, which include 

 those concerned directly with the maintenance of the individual, 

 such as digestion, respiration, circulation, etc. ; 2. Nervous Func- 

 tions, which include those that bring the different organs of the 

 body into harmonious relations with one another, and, in addition, 

 bring the individual, through the special senses sight, hearing, 

 etc. into relation with the world outside him ; and 3. Reproductive 

 Functions, which are concerned not with the individual, but with 

 the species, which they perpetuate. 



Histology of the Human Body. Anatomy, as we have 

 already learned, is the science which treats of structure ; and this 

 is true as well of the minute or microscopic as of the gross or 

 macroscopic structure ; but it will be of advantage to the student 

 of physiology to have distinctly in mind so much of the histology 

 or minute structure of the body as is necessary to a full under- 

 standing of its functions, and to appreciate the discussion of them. 

 With this end in view, the histology of each organ will be given 

 in connection with its function, but preliminary to all this we shall 

 discuss the tissues of the body which go to make up these organs. 

 For fuller details the student is referred to the many excellent 

 treatises on human histology. 



Physiologic Chemistry. Although physiology, strictly 

 speaking, has nothing to do with composition, still, as a matter 

 of necessity as well as of convenience, it is usual to preface the 

 study of the functions of the human body with a greater or lesser 

 consideration of its composition. This consideration is necessary, 

 because, as a rule, medical students have an insufficient knowledge 

 of this branch of chemistry physiologic chemistry to take up 

 at once the study of the functions with profit, and should the 



