32 CLASSIFICATION 



freedom of movement; is permitted, the cup being much deeper 

 and the union by fibrous bands more intimate. 



The lower end of the femur helps to form the hinge -like 

 knee-joint in conjunction with the shin-bone (tibia) of the lower 

 leg, which corresponds to the radius in the forearm. The front 

 of this joint is protected by a round and somewhat flattened 

 bone, the patella or knee-pan. There is nothing corresponding 

 to this in the elbow. 



The chief bone of the lower leg is the tibia; but there is 

 also a second much slenderer one, the fibula, corresponding to 

 the ulna in the forearm, but not helping to form the knee- 

 joint. Just as the wrist is supported by a number of irregular 

 bones, so is the ankle, but as these have to support the weight 

 of the body they are relatively much larger and stronger. 

 Following them come five sole -bones, corresponding to palm- 

 bones; while the toes, like the fingers, are completed by fourteen 

 phalanges, which, however, are relatively short. The great toe 

 is not opposable and is very much larger than the others, since 

 it plays an important share in supporting the weight of the 

 body. It may be remarked that the skeleton of the foot pre- 

 sents an arch from before backwards, and another from side to 

 side, an arrangement which combines great strength with a large 

 amount of springiness. The weight of the body falls mainly on 

 the heel, toes, and outer side of the foot. 



NUTRITION. 



The body is constantly undergoing waste, and also, in the 

 earlier part of life, increasing in volume, or growing. This waste 

 must be counterbalanced and materials for growth provided; 

 hence the necessity for food, which may be compared to the 

 materials used for repairing a machine and, it may be, making 

 additions to it. And just as the original nature of a machine 

 determines the material to be employed, so also in the case of 

 the body. In other words, if we are to understand the nature 

 of the food, we must have some knowledge of the composition of 

 the body. 



Chemical Composition of the Body. — When the body of 

 an animal is acted upon by intense heat most of it is dissipated 

 in the form of gas, the comparatively small remainder, or ash, 

 consisting of various mineral matters. The gaseous portion, when 



