170 STUDIES IN PHYSIOLOGY 



The Pelvic Girdle. A complete girdle of bones is formed 

 at the posterior end of the trunk by the two pelvic bones 

 which are attached dorsally to the sacrum and which meet 

 in front. The upper edge of these bones can be felt at the 

 hips (Fig. TO, 'if). On the outer side of each pelvic bone is 

 a deep socket (Fig. 70, acet) into which fits the proximal end 

 of the femur. Since the pelvic girdle is not movable like 

 the pectoral, the body has a firm base Of support. The 

 range of movement of the leg, however, is relatively small 

 in comparison with that of the arm. 



3. THE SKELETON OP THE HEAD 



Two groups of bones may be distinguished in the skull or 

 skeleton of the head, namely, the bones forming the cranium 

 which surrounds and protects the brain, and the bones that 

 form the skeleton of the face. 



The Bones of the Cranium. The cranium is a more or less 

 spherical box, composed of eight bones as follows: The 

 fron'tal (Latin frons, frontis = forehead) forms the forehead 

 and the top of the eye sockets. A pair of pa-ri'e-tal bones 

 (Latin paries, parietis = a wall) make up the principal part of 

 the side walls of the cranium and meet along the top of the 

 skull. On each side below the parietals, lies one of the tem'- 

 po-ral bones. The temporal bones contain the cavities in 

 which lie the most delicate parts of the ear. The oc-cip'i-tal 

 (Latin ob = against + caput = head) forms the posterior part 

 of the dorsal region of the brain box. In this bone is 

 a large opening, the fo-ra'men magnum (Latin magnum = 

 great + foramen hole), through which the spinal cord 

 passes to connect with the brain. The sphe'noid is a very 

 irregular bone shaped more or less like a butterfly; this 

 with the eth'moid makes a floor for the cranium, and in 

 front toward the ventral surface separates the brain from 

 the nose cavity. The brain is therefore inclosed by two 

 pairs of bones (the parietals and temporals) and by four 



