THE HUMAN ORGANISM 291 



money they have in watching others play instead of getting into 

 the games themselves. That may be good business, but it is not 

 good health, either for the body or for the spirit, when carried 

 too far. For many people dancing is a good form of exercise, 

 because it may be carried on in connection with sociability 

 and the rhythm of music. 



Muscular development is a good indication of the general 

 health of the body, but under conditions of modern living we 

 need quick, responsive muscles rather than large, tough ones. 



THE HUMAN BODY AND KEEPING IT FIT 



1. Knowledge about the structure of the human body 



Value of such knowledge 



A frequent subject of discussion 



Knowledge related to management 



Common interest in health 

 How such knowledge is obtained 



Direct observation (external features) 



Dissections by anatomists 



Dissection of other animals (in part) 



Preparations; models; pictures 



2. General plan of vertebrate structure 



Main axis 



Thorax and abdomen 

 Skeleton 

 Body wall 

 Internal organs 

 Dorsal cavity 

 Spinal cord 

 Ventral cavity 



Lungs (gills) Kidneys 



Heart Bladder 



Esophagus Reproductive organs 



(Diaphragm, in mam- Female 



mals only) Ovary 



Stomach Oviducts etc. 



Intestines Male 



Liver Spermary 



Pancreas ' Sperm ducts etc. 



