56 



ANATOMY FOR NURSES 



[Chap. V 



"^^ 



Fig. 25. 



Pariet.\l Bone. Inner surface. ^4, parietal depression; E, fur- 

 row for ramification of arteries. 



ward and forms the mastoid process. This process is filled with 

 a number of connected cancellous .spaces, containing air, and 

 called mastoid cells.' They communicate with the cavity of 

 the middle ear. The condition known as mastoiditis means in- 

 flammation of the lininj: of these cells. 



Supraorbital 

 Margin 

 Roof of 

 Orbital Cavity 



' Cells. — The student must bear in mind that the word cell is used with two 



different meanings in anatomy. Histologically speaking, the word "cell" refers to 



one of the component units of the body, such as an "epithelial cell" or "nerve cell." 



In connection with the use of the words "mastoid cells" in the text, the word 



"cells" refers to tiny enclosed hollow chambers similar to the cells of a honey-comb. 



