PART II. 
Outlines of Anatomy and Physiology. 
CHAPTER L 
THE SKELETON. 
The anatomy and physiology contained in this and the following 
chapters is merely intended to convey a general knowledge of the 
animaFs structure, the position of the various organs and their 
functions, sufficient for the reader unacquainted with these subjects 
to recognize the structures probably affected in such injuries or 
diseases as may come under his observation. 
External form is dependent upon an internal basement structure. 
This consists of a number of definitely but diversely shaped masses 
of a hard substance called bone. This basement structure is known 
as the skeleton. The bones entering into its formation are of 
various forms and sizes, depending on the uses for which they are 
intended. They are divided into four classes : long, short, flat and 
irregular. The first named are situated in the limbs ; they have a. 
shaft and two extremities. Examples : — Arm bone (humerus), thigh 
bone (femur). The scapula or shoulder blade, pelvis, and frontal 
bones of the head are examples of flat bones. The bones of the 
vertebral column are examples of the irregular type of bones, and 
those of the knee and hock are short bones. Bone is a tough, hard, 
elastic substance consisting of animal matter impregnated with 
earthy salts. The earthy salts may be removed from the bone by 
immersion in dilute hydrochloric acid ; the figure of the bone remains 
unchanged, but instead of being hard, it will be found to resemble 
cartilage or grizzle, and may be twisted in any direction. The 
composition of bone is as follows : — 
Earthy matter 
Animal matter 
Total ... loo'o 
{Ashby). 
The ends of the bones are constructed in different ways to 
permit of more or less motion. In some parts there is a ball and 
socket arrangement ; in others, hinge-like joints, and so on. 
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