INTRODUCTORY 23 



prominent by being- thicker in the middle ; thus the articular surfaces 

 on a dried bone, from which the cartilages have been removed, differ 

 in shape and size from the corresponding surfaces on a fresh bone. 

 (b) The uniting capsular ligament is a more or less tubular structure 

 fastened by its edges to the bones, often at some little distance from 



FIG. 8. 



Synovial Membrane.J|^ ^% Mf Ligament ' 



Synovial Cavityx^lf |$$Wticular Cartilage. 



xx 



-Periosteum. 



DIAGRAM OP A DIARTHROSIS. 



the actual articulating surfaces ; it thus encloses (c) the cavity of the 

 joint, which is known as the syno'vial cavity, because it is (d) lined 

 by a delicate synovial membrane which secretes (e) the synovia, 1 the 

 lubricant of the articulating surfaces. 



Joints are rendered more complicated when a pad, or several pads, 

 of cartilage are interposed between the articulating surfaces of the 

 bones, or when a ligament within the joint passes from one bone to the 

 other. 



GENERAL CHARACTERS OF BONES. 



DRIED BONE. If the student examine one of the long bones which 

 has been cleaned and dried, the following general characters will be 

 observed : 



Color. Normally the color of a dried bone is yellowish white. If, 

 however, it has been exposed for some time to the sun or to certain 

 chemicals, it will be bleached to a bluish white or chalk color, and if, 

 moreover, it has not been thoroughly cleaned, it will be more or less 

 brown. Bones are sometimes accidentally colored during the process 

 of maceration ; they turn black if macerated in an oaken vessel in 

 the presence of iron ; or red or blue if taken from animals injected 



1 From (Gr.) syn, together, and ovum, an egg ; resembling the white of egg. 



