74 



ELEMENTS OF PHYSIOLOGY 



HYGIENE OF SKELETON 



121. Nourishment of Bones. If a limb be disused be- 

 cause of paralysis or long sickness, the bones, as well as 

 the soft parts, lose in strength and weight. This shows 

 that the more vigorous circulation which comes with exer- 

 cise helps to repair the osseous tis- 

 sue (Fig. 70). The blood vessels 

 that supply the bones enter from 

 the inner side of the periosteum. 

 We thus see why the bone shrinks 

 away if the periosteum is removed, 

 and why the surgeon is careful to 

 leave as much of the periosteum as 

 possible in the case of bones splin- 

 tered by accidents. 



The animal matter of bones is 

 most abundant in childhood, and 

 a child's bones will bend before 

 they break. If broken, they heal 

 rapidly. The animal matter is less 

 abundant in the aged, therefore 

 the bones are brittle, more easily 

 broken, and take longer to heal. 



122. Broken Bones. The two 

 ends of a broken bone should be 

 brought together in their correct 

 position as soon as possible, before 

 inflammation and swelling render 

 this difficult. Of course a surgeon should be called to set 

 a broken bone. If the patient has to be carried some dis- 

 tance, care should be taken to prevent injury to the fleshy 

 parts by the ends of the fractured bone ; the limb should 

 be bound with handkerchiefs to a strip of board, or even 

 to umbrellas or walking sticks, as temporary splints 



FIG. 70. Haversian Canals in 

 Compact Tissue of Bones, 

 with their Connecting Cana- 

 liculi and the Lacunae. Mag- 

 nified 200 Diameters. 



The bone is cut lengthwise. Com- 

 pare with Fig. 44 where the bone 

 is shown cut across ; why are 

 fewer canaliculi cut apart in Fig. 

 44 than in Fig. 70? 



