62 ELEMENTARY PHYSIOLOGY 



4. What is the abdomen f Describe the nature of its walls. 



5. Give a short description of the diaphragm. 



6. Describe briefly each of the following : intercostal muscle, thorax, midriff, 



and abdomen. 



LESSON XL 

 THE ANATOMY OF THE FACE AND NECK. 



IT will be advisable to study the anatomy of the face and neck 

 before learning the nature, of the organs contained in the thorax 

 and abdomen, as by adopting this plan we shall be able to under- 

 stand better the connection between the organs of the face and 

 those of the two divisions of the great body cavity. 



The accompanying diagram exhibits a medial section of the 

 face and neck, that is, a section carried from the tip of the nose 

 backward, thus cutting through the middle of the cervical portion 

 of the vertebral column. 



We first proceed to note the positions of the chief bones of 

 the face, &c., as exposed in this section ; and we again remind the 

 student of the advantage to be gained by comparing the structure 

 of the human face and neck with that exhibited in a similar section 

 of the head of some small animal. 



The sphenoid bone separates the upper and back portion of 

 tne cavity of the nose from the cavity of the skull. 



The ethmoid bone separates the same two cavities more to- 

 ward the front. 



The nasal bones form the upper and hard portion of the ridge 

 of the nose, the lower portion of which is constructed of cartilage, 

 and is therefore flexible. 



The cavity of the nose is limited below by the superior maxil- 

 lary bones, and the palatal bones behind them ; these forming 

 together the hard palate. 



It will thus be seen that the nasal cavity occupies a very large 

 proportion of the face. It is divided centrally from front to back 

 by the thin bony plate called the vomer, and its outer or right 

 and left walls are formed by the superior, middle, and inferior 

 turbinated or scroll-like bones, the upper two of which form part 

 of the ethmoid bone, while the lower or inferior are distinct bones. 



Below the nasal cavities, and separated from them by the hard 

 palate, is the cavity of the mouth. The roof of the mouth is con- 

 tinued backward from the hard palate by the soft palate, which is 

 composed of fleshy substance, without any kind of hard support ; 

 and behind this the cavities of the mouth and nose both lead into 

 a cavity called the pharynx. 



