ELEMENTS OF PHYSIOLOGY 



and blood vessels. If we remove the periosteum from the 

 surface, the red marrow from the pores, and the yellow 

 marrow from the larger cavity, we have remaining the true 

 bony substance. Yet even this is not one substance, but 

 consists of animal matter and mineral 

 matter in the proportion of two parts of 

 the former to one of the latter. The 

 animal matter is gelatin, like the sub- 

 stance composing the white fibrous part 

 of connective tissue. The mineral mat- 

 ter is chiefly phosphate of lime and 

 carbonate of lime. Can you describe 

 the microscopic structure of bony tis- 

 sue as shown in Fig. 70? The mineral 

 matter may be removed by soaking the 

 bones for several days in strong vinegar or 

 in dilute muriatic acid. The bone is then 



flexible but tough. 



If a slender bone, 



as a hog's rib, has 



been used, it can 



be tied in a knot; 



after the acid has 



been washed off, it FlG . 67 . - shin-bone 



may be preserved < tibia ) sawed in two 



in dilute alcohol as 



a curiosity. The 



animal matter may 



be removed by 



FIG. 68. Side and Under holding the bone 

 View of a Vertebra. i . , , 



on a shovel in the 



Is it a cervical, a thoracic, or alum- r __ . .. . .. . 



bar vertebra? (See Fig. 69.) fire for a Sufficient length of time. 



The mineral part remaining is very 



light and brittle, and weighs only one third as much as the 

 original bone, the form of which it still preserves. 



along its Length. 



2, struts and stays of 

 spongy bone support- 

 ing 7, the upper and 

 lower articular sur- 

 faces; 3, compact bone 

 forming the shaft ; 

 4, marrow cavity ; 

 6, periosteum. 



