THE TISSUES 13 



a filamentous substance, which yields abundant gelatine 

 on being boiled, and is the matter which tans when hide is 

 made into leather. This is called connective tissue, ^ 

 because it is the great connecting mediuni by which the 

 different parts of the body are held together. Thus it 

 passes from the dermis between all the other organs, en- 

 sheathing the muscles, coating the bones and cartilages, 

 and eventually reaching and entering into the mucous 

 membranes. And so completely and thoroughly does the 

 connective tissue permeate almost all parts of the body, 

 that if every other tissue could be dissected away, a com- 

 plete model of all the organs would be left composed of this 

 tissue. Connective tissue varies very much in character ; 

 in some places being very soft and tender, at others — as in 

 the tendons and ligaments, which are almost wholly com- 

 posed of it — attaining great strength and density. 



Among the most important of the tissues imbedded in 

 and ensheathed by the connective tissue, are some the 

 presence and action of which can be readily determined 

 during life. 



If the upper arm of a man whose arm is stretched out 

 be tightly grasped by another person, the latter, as the 

 former bends up his fore-arm, will feel a great soft mass 

 which lies at the fore part of the upper arm, swell, harden, 

 and become prominent. As the arm is extended again, 

 the swelling and hardness vanish. 



On removing the skin, the body which thus changes its 

 configuration is found to be a mass of red flesh, sheathed 

 in connective tissue. The sheath is continued at each 

 end into a tendon, by which the muscle is attached, on 

 the one hand, to the shoulder-bone, and, on the other, to 

 one of the bones of the fore-arm. This mass of flesh is 

 the muscle called biceps, and it has the peculiar pro- 

 perty of changing its dimensions — shortening and be- 

 coming thick in proportion to its decrease in length — when 



1 Every such constituent of the body, as epidermis, cartilage or 

 muscle, is called a •' tissue." CSee Lesson XII.) 



