CHAPTER Lk 
THE STRUCTURE AND FORMATION 
OF BONE. 
Connective Tissues.—Those tissues, whose func- 
tion it is to serve as connecting, supporting, or skeletal 
substances are known as connective tissues; and 
include such forms as areolar, elastic, fibrous, retiform, 
lymphoid and adipose tissue, cartilage and bone; all 
of which are derived from the mesoblast. It is with 
these two last mentioned substances—cartilage and 
bone—that we are at present more directly concerned. 
Cartilage, in mass, is a yellowish or bluish-white 
elastic tissuc, the cells of which are imbedded in a firm 
eround substance, or matrix. Excepting on those 
surfaces articulating with some other part of the body, 
it is usually covered by a fibrous connective tissue 
the perichondrium, which is richly supplied with 
blood-vessels, lymphatics and nerves. No nerves pass 
into the substance of the cartilage; at 1s, thereierc, 
non-sensitive. 
Cartilage contains a substance known as chon- 
drigen, which yields on boiling chondrin, a mixture of 
