CLASSIFICATION OF THE BONES. 15 



For the two lower extremities, sixty-six bones ; on each side 

 one femur, a tibia, a fibula, patella, seven ankle or tarsal bones, 

 five metatarsal, fourteen phalanges of the toes, and two and some- 

 times three sesamoid. Thus according to the enumeration of 

 Marjolin, there are two hundred and fifty-two bones in the human 

 body. The number of sesamoid bones, however, is very varia- 

 ble ; and some anatomists of high reputation, do not include the 

 teeth in the enumeration of the bones of the body. 

 The bones are all either symmetrical or unsymmetrical. 

 The symmetrical bones are in pairs, and correspond in size 

 and shape very nearly with each other, and are placed upon 

 either side, like those of the extremities and ribs. The unsym- 

 metrical, which consist of some of the bones of the head, the 

 sternum, vertebrae, sacrum, os coccygis and os hyoides, are 

 situated in the middle line of the body. The lateral halves of 

 these bones correspond very closely with each other. 

 From their general form and geometrical dimensions, the 

 bones have been divided into classes ; the long bones, ossa 

 longa, the broad bones, ossa lati, and the thick bones, OSSQ, 

 crassa. The long bones, occupy the centre of the limbs, are 

 the levers used in locomotion, and form a series of "broken 

 columns, articulated together, which increase in number, and 

 diminish in si^e, as they recede from the trunk. They are 

 divided into a middle part, body or diaphysis ; and into extre- 

 mities or epjphyses. The body is cylindrical in some, prismatic 

 and triangular in others, and generally a little curved or twisted. 

 The extremities are expanded and thick. The bodies which 

 are the smallest part, happily correspond with the bellies or 

 largest .part of the muscles the extremities with their narrow 

 tendinous terminations. 



The broad bones assist in forming a part of the walls of the 

 trunk and head ; they are flattened, more or less concave on 

 their interior, varied in their form, and thicker usually at their 

 margins, than at their centres. 



The thick bones are assembled in masses, and form parts at 

 once solid and moveable as in the spinal column, the wrist, and 

 the ankle. 



