1 66 Human Physiology. 



anism. The knee-joint is furnished with a bone unconnected 

 with any other, the patella, which protects, strengthens, and 

 beautifies the joint. There is also a disconnected bone at the 

 root of the tongue. 



I do not purpose to go fully into the anatomy of the human 

 body, giving only so much as may be necessary to illustrate 

 its physiology; but there are a few points of great interest in 

 connection with the bony skeleton, with its cushions and stays, 

 its light firm rods, broad strong plates, elastic arches, and gen- 

 eral union of firmness and flexibility. Observe the number of 

 movements that can be given to the lower jaw; the great sweep 

 of the shoulder joint; the rotation of the arm notwithstanding 

 the firm hinge-joint at the elbow; the flexible curvings of trie- 

 wrist; the admirable hand, with all its capabilities. The brain 

 is enclosed in a perfect box; the eyes have deep and very hard 

 bony orbits to protect them ; the nasal bones guard the organ 

 of smell, and give to the face its most important feature; while 

 the organ of hearing, not the external ear, is completely embed- 

 ded in the centre of one of the hardest bones in the body. 

 Consider then the hip-joint, where an almost round ball on the 

 thigh-bone is bedded in a deep cup-like cavity, held there by a 

 strong round ligament, held again by a strong covering capsule, 

 and held and moved by a great mass of the strongest muscles 

 in the body; yet I have seen a girl of fifteen, standing grace- 

 fully erect on one foot, raise the other above her shoulder, till, 

 without bending her body or touching her leg with her hand, 

 she drank from a glass which she had placed upon the sole of 

 her foot, and this performance, done apparently with perfect 

 ease, was as graceful as it was a wonderful exhibition of flexi- 

 bility and trained muscular power. 



The bones are moved by muscles. A muscle is a collection 

 of small fibres of flesh in a sheath. Each fibre is made of 

 numerous smaller fibres, which are composed of cells or disks, 

 and it is the widening or contraction of these disks which 



