22 



THE FRAMEWORK OF THE BODY 



present in the bones whose position exposes them to accident. 

 (Head Note 4.) 



6. The Skeleton. The number of bones in the human body 

 exceeds two hundred, and when joined together in their proper 

 places, they form what is termed the Skeleton (Fig. 2). It 

 embraces three important cavities. The first of these, sur- 

 mounting the frame, is a box of bone, called the skull; below 

 this, is a bony case, or " chest ; " and lower down is a bony 

 basin, called the pelvis. The two latter compose the trunk. 



FIG. 5. RIBS IN A NATURAL AND 

 HEALTHY STATE 



FIG. 6. RIBS SHOWING THE EFFECTS 

 OF TIGHT LACING 



The trunk and skull are maintained in their proper relations 

 by the " spinal column." Branching from the trunk are two 



4. Experiment. Obtain one of the long bones of the sheep or calf, 

 scrape it thoroughly clean, but do not detach the cartilage covering the 

 ends. Saw it through crosswise in the middle ; then saw the upper half 

 through lengthwise. (See Fig. 1.) 



The transverse section shows the compact, hard outer layer, enclosing 

 the soft pulp or marrow. 



The longitudinal section shows, at its upper end, the layer of cartilage, 

 its thickness and intimate connection with the bone ; the outer layer of 

 bone here is thinnest and gradually increases toward the middle of the 

 shaft, where it is thickest; the central canal, containing the marrow, 

 becomes smaller as it approaches the head of the bone, where it is lost in 

 the dense network of bony structure. The latter is best demonstrated by 

 holding the cut surface for a while under a faucet, so as to wash away the 

 blood, etc., contained in the meshes. It will now be seen that these 



6. Number of bones ? Skeleton ? The skull ? Chest ? The trunk ? The trunk and 

 skull, how maintained ? What of the arms ? Legs ? 



