CHAP. IV.] THE SKELETON. 35 



the projections of the crest of the ilium in front, above and 

 below, the two upper or superior spinous processes being in par- 

 ticular well known and convenient landmarks used by surgeons 

 in making anatomical measurements ; (2) the largest foramen 

 in the skeleton, known as the door-like or thyroid foramen, sit- 

 uated between the ischium and pubes ; and (3) the symphysis 

 pubis, or pubic articulation, which also serves for a convenient 

 landmark in making measurements. 



The patella, or knee-cap, is a small, flat, triangular bone, placed 

 in front of the knee-joint. It is generally regarded as analogous 

 to the olecranon process of the ulna, which also occasionally 

 exists as a separate piece of bone. The knee-cap serves to pro- 

 tect the front of the knee-joint. 



Irregular bones. The irregular bones are those which, on 

 account of their peculiar shape, cannot be grouped under either 

 of the preceding heads. 



Irregular bones of the head : 



Temporal 2 



Sphenoid 1 



Ethmoid 1 



4 



The temporal bones are situated at the sides and base of the 

 skull. They are named temporal from the Latin word, tempus, 

 time, as it is on the temple the 

 hair first becomes gray and thin, 

 and thus shows the ravages of 

 time. The temporal bones are 

 divided into three parts : the 

 hard, dense portion, called pe- 

 trous ; a thin and expanded 

 scale-like portion, called squa- 

 mous ; and a mastoid portion, 

 which is perforated by numerous 

 holes and contains a number of FlG 32. TEMPORAL BONE. Outer 



Cells. The internal ear, the es- surface. 1, squamous portion ; 7, ex- 

 , . , . , , , ternal opening of auditory canal m 



sentiai part ot the organ 01 near- petrous portion ; 8, mastoid portion ; 3, 



ing, is Contained in a Series of glenoid cavity for reception of condyle 

 ., _ . . of lower jaw. 



cavities, channelled out of the 



substance of the petrous portion. Between the squamous and 



