JOINTS 



3167 



JOINT STOCK COMPANY 



the China Sea, is pleasant and healthful. The 

 surface of the country is broken by a few hills, 

 the highest, Mount Ophir, being 4,186 feet 

 above the sea. The land is densely wooded 

 and tropical fruits grow plentifully. Johore 

 Bahru, the capital, is a city of about 20,000 

 inhabitants, and is sometimes called the "Monte 

 Carlo of Asia." It is much visited by the 

 people of Singapore, fifteen miles farther south, 

 whose climate is much warmer. Johore has 

 one railroad, connecting with a main line about 

 120 miles farther north. The exports, rubber, 

 coffee, black pepper, gambier, gutta-percha and 

 sago, yield the state a large revenue. 



JOINTS, which are formed by the meeting 

 of two bones, are chiefly for the purpose of 

 making the limbs and other parts of the . body 

 flexible and affording freedom of movement. 

 They are an important factor in the countless 

 acts that one performs- every day. In regard 

 to their structure, joints are said to be im- 

 movable and movable. 



Immovable Joints. These are placed where 

 the bones are almost directly in contact with 

 each other, separated only by a thin layer of 

 connective tissue. Examples are the joints 

 connecting the bones of the skull. Ordinarily 

 these joints are stationary, but in case of acci- 

 dent they may move enough to prevent the 

 breaking of a bone. The cranium joints there- 

 fore help protect the brain, one of the most 

 delicate organs of the body. 



Movable Joints. The movable joints are 

 found for the most part in the limbs, and are 

 divided into three classes. Hinge joints are 



JOINTS 



(a) Hinge joint; (6) ball and socket joint; 

 (c) pivot joint. 



those which permit a forward and backward 

 motion in one plane, like the motion of a door 

 on its hinges. The joints at the elbow and 

 knee and the last two joints of the fingers are 

 typical examples. Pivot joints give the move- 

 ment of rotation, such as the motion of the 



head in turning from side to side. The joints 

 which allow the greatest freedom of movement 

 are the ball-and-socket. Important examples 

 are those at the hip and the shoulder. In each 

 case there is an enlarged and rounding end of 

 a long bone (ball) fitting into a hollow of 

 another bone (socket). The arms have a 

 greater range of motion than the legs because 

 the shoulder socket is more shallow than the 

 hip socket, but the shoulder is more easily dis- 

 located, that is, "put out of joint." 



Movable joints are safeguarded in several 

 ways. Wherever two bones glide over one 

 another there is a layer of elastic cartilage, or 

 gristle, on the end of each bone (see CARTI- 

 LAGE). Ease of movement is secured by the 

 smoothness of the cartilage, and its elasticity 

 serves -to break the force of sudden jars. All 

 movable joints are supplied with a lubricating 

 substance called synovial fluid, which keeps the 

 cartilages smooth and prevents the bones from 

 feeling the wearing effects of constant move- 

 ment. Bones are held in place at the joints 

 by strong ligaments, which are fastened to the 

 bones above and below the joint. At the hip 

 there is a cdllarlike set of ligaments which 

 form a capsule about the joint. 



Joints are subject to sprains and dislocations. 

 A sprain (which see) occurs when the liga- 

 ments about a joint are torn or badly stretched. 

 Serious sprains are extremely painful and if 

 neglected may result in stiffening of the joints. 

 Dislocated joints should have the attention of 

 a physician, that the bones may quickly be 

 put back in place. 



The painful disease popularly known as 

 rheumatism often settles in the joints, and the 

 chronic form of this ailment usually cripples 

 the patient. Gout is a painful disease of the 

 joints. See GOUT; RHEUMATISM. S.C.B. 



JOINTS, in ecology, are the cracks which 

 separate rocks into more or less regular blocks. 

 They are usually parallel and in systems, so 

 the rock seems to be divided as evenly as 

 though the work had been done by an archi- 

 tect. Basaltic columns of trap rock form excel- 

 lent illustrations of such divisions. Joints are 

 usually caused by earthquakes, and the frac- 

 ture of rocks from cooling or drying. They 

 may affect the drainage of the region and also 

 the flow of springs by stopping or changing 

 the outlet. This is why an earthquake some- 

 times causes some springs to dry up and new 

 ones to break forth. 



JOINT STOCK COMPANY, in Great Britain, 

 Canada and the other British dominions, cor- 



