TISSUES. 85 



Bone tumors are not uncommon and are called 

 osteoma. They are of slow growth, usually as- 

 sociated with bone, and harmless. 



On account of the great vascularity, a broken bone 

 heals more rapidly than a broken tendon, or liga- 

 ment, or a broken cartilage. An old bone is brittle 

 and the healing process a slow one on account of the 

 increase of earthy matter and a decrease of the 

 organic. 



An infection beneath the periosteum is a felon. 

 The periosteum is firmly attached to the bone by 

 Sharpey's fibers and the pressure produced by an in- 

 fection beneath it gives rise to extreme pain, which 

 is instantly relieved by an incision. An inflam- 

 mation in the bone is called an ostitis, while if it is 

 located in the marrow cavity it is called an osteo- 

 myelitis. 



III. MUSCULAR TISSUE. 



Muscular tissue consists of elongated cellular ele- 

 ments in which contraction takes place along the 

 long axis of the cell. This contraction is intrinsic to 

 the muscle cytoplasm, and of this the spongioplasm 

 seems to be. the active agent. The word sarcode and 

 its derivatives is used in describing muscle proto- 

 plasm. This word was introduced by Dujardin, in 

 1835, and was later replaced by the word protoplasm. 



i. Smooth, Non-striated or Involuntary Muscle. 

 This is the simplest form of muscle tissue. The cells 

 are mononucleated, elongated, or spindle-shaped, 

 and vary in length from 40 to 200 //. The nucleus 

 occupies the center of the cell, is rich in chromatin, 

 and oval, with blunt ends, or cigar-shaped. The 



