72 OSTEOLOGY 



plate of the palate; inner wall, by the nasal process 

 of the maxilla, lacrymal, ethmoid, and body of the 

 sphenoid; outer wall, by the malar and frontal and 

 great wing of the sphenoid. 



The Nasal Fossa or Cavities. These are placed one 

 on each side of a median vertical wall. They open in 

 front by the anterior nasal aperture (nares) and behind 

 by the posterior nares. They communicate with the 

 sinuses (air spaces) of the frontal, sphenoid, and antruin 

 of Highmore, the latter is in the body of the maxilla, 

 and the ethmoidal cells. Thus the danger from infec- 

 tion entering these air spaces following an abscess for- 

 mation, influenza, etc., may readily be understood. 



THE VERTEBRAL COLUMN AS A WHOLE 



The vertebral or spinal column is a central axis upon 

 which other parts are arranged, situated in the median 

 line at the posterior part of the trunk; above it sup- 

 ports the head, by having the first vertebra receive 

 the condyles of the occipital bone; laterally, the ribs, 

 and it rests on the sacrum. It is made up of thirty- 

 three separate vertebrae, imposed one upon the other 

 with an intervertebral layers of cartilages between 

 each one, and held in firm relationship by means of 

 ligaments. 



The vertebrae are divisible into seven cervical, 

 twelve thoracic, five lumbar, five sacral, and four 

 coccygeal. The cervical, thoracic, and lumbar verte- 

 brae remain separate throughout life, and are known 

 as true or movable vertebrae; but the sacral and coccy- 

 geal vertebrae are firmly united in the adult, so as to 

 form two bones five entering into the formation of 

 the sacrum and four into the terminal bone of the 

 spine or the coccyx. The sacral and coccygeal verte- 

 bras are called the immovable vertebrae. 



The average length of the vertebral column is about 



