Co-ordination of Subjects 37 



The ability to analyze any product or portion of the body must lie 

 with analytical chemistry, while the study of how to build up new 

 products comes under synthetic chemistry. All digestion takes place by 

 enzymes, and the enzymes of the stomach, for example, will not function 

 unless they are placed in an acid- medium, such as the gastric juice. 

 Changes in food, or abnormalities of various kinds, may cause an excess 

 of this acid, or may prevent a sufficient quantity of the proper quality 

 being formed — all such changes are chemical. 



The sttidy of physics in its application to one's body is not so self- 

 evident and is often the bug-bear of students. Unfortunately most text- 

 books on physics lay stress upon mechanical laws only in their indus- 

 trial applications, and fail to show how these same laws apply to the 

 human body. 



The mechanics of the living body are, however, quite similar and 

 much more important than all the industrial applications which can be 

 found. 



The three types of levers with the fulcrum in different positions are 

 the same in the body (Fig. 2) as they are in general mechanics. A 

 knowledge of the exact points where stress and pull are applied, with a 

 consequent ability to "figure out" where new growth-structures will 

 develop, is of prime importance in broken, misplaced, and re-set struc- 

 tures, if the patient is not to suffer untold agony and sorrow in future 

 years. 



In this connection, the laws governing pulleys, the combination of 

 rolling and sliding movement of joints, as well as the principles of 

 gravity, must be thoroughly understood ; for, it is simply and solely on 

 these principles that the various movements of the body can take place, 

 and consequently, it is only a knowledge of such principles which can 

 in turn make possible the correction of abnormalities of joints. 



The principles governing friction are applied in the correction -of 

 both internal and external injuries, while experimental physiology would 

 be impossible without a knowledge of centripetal and centrifugal forces 

 and the laws governing liquid and gaseous pressures. 



The laws governing liquids apply throughout the entire body in 

 great detail, for there is scarcely a spot as large as the point of a needle 

 in the body that liquid nourishment (blood or lymph) does not enter. 

 Pressure in any region causes swelling, varicose veins, dropsy, and a 

 host of other ills ; while bed-sores are nothing more or less than the 

 effect of continued pressure of blood in the same vessels of the side or 

 back on which the person lies, gravity causing the blood to sink to the 

 lowest level and be held there. 



An understanding of the difference in densities makes possible many 

 physiological experiments, which w r ould otherwise result fatally to the 

 patient. A solution, if it is to be injected, must not only have the proper 

 density so as not to cause a too rapid change in the blood, but the whole 



