34 



HITCHCOCK'S ANATOMY 



Lacunse of Bone, a, central portion, 

 canaliculi or Bone Pores. 



0 o„ 



Fig. 32. seen in Fig. 32. These 



rays are minute canals, 

 and nearly all of them 

 anastomose, or have com- 

 munication with each other. 

 They are called Canaliculi, 

 or Bone Pores, and mea- 

 sure soiooth of an inch 

 in diameter. 



87. Ultimate Granules. — The ultimate histological ele- 

 Fig. 33. ment, or the smallest element of bones as yet 



discovered, is made up of pale oval granules, 

 about e oV oth of an inch in diameter. These 

 granules constitute all the substance of the bone 

 $^ti!3w except the minute vessels already mentioned. 



88. Hence the microscopic elements of bone are four : 



1. Haversian Canals. 



2. Lacunae or Bone Corpuscles. 



3. Canaliculi or Bone Pores. 



4. Ultimate Granules. 



89. Periosteum. — In all parts of the body, both solid and 

 fluid, we find that nature has made ample protection by * 

 providing for nearly every organ a firm membranous sheath. 

 This not only serves as a protection and support, but in 

 many cases a means of nutriment. Upon the bones ac- 

 cordingly we find a very firm whitish yellow membrane 

 closely attached to them in most places, and very smooth, 

 called the Periosteum. This occurs on every part of every 

 bone, except at the articulations, and upon the crowns of the 

 teeth. It is, when healthy, perfectly insensible, and contains 

 the vessels which ramify into the bones, being in fact the 



What are the Bone Pores or Canaliculi ? 87. What is the smallest or ultimate element 

 of bones ? 83. Give the four microscopic elements of bone. 89. What is the color of 

 the Periosteum? On what part of the bones is it wanting? What two important 

 purposes does it subserve f 



