38 LABORATORY WORK. 



fossa, in which fits the head of the first bone (humerus) of 

 the arm. Has a joint like this much freedom of motion? 

 The bone of the forearm is the radio-ulna. Does it show 

 any signs of a double condition? With what does it con- 

 nect below? How many bones in the wrist (carpus)*? 

 How are they arranged? How many in the palm (meta- 

 carpus) and in each finger (digit) 1 } How does the thumb 

 differ from the others? 



On the outside of each half of the pelvic girdle is a 

 deep cup (acetabulum) , in which is the head of the thigh- 

 bone (femur). Below this comes the tibio-fibula. Is this 

 double? Below this comes the ankle region (tarsus). The 

 first two bones of this are long, the second very short. 

 What effect does this have on the position of the heel 

 (p. 33)? Compare the tarsus with the carpus. Is there 

 anything which you could call a sixth toe? Does it come 

 on the inside or outside of the foot? 



In the skull make out an axial portion (cranium) ex- 

 panding in front and behind to support a bony arch 

 below the eye, and attached to the cranium behind, the 

 lower jaw (mandible). At the posterior end of the skull 

 is the large opening (foramen magnum) through which the 

 spinal cord connects with the brain. On either side of the 

 foramen is a protuberance (occipital condyle) by means of 

 which the skull articulates with the first vertebra (atlas). 

 These condyles are borne on the exoccipital bones, the rest 

 of the border of the foramen is formed of cartilage. (In 

 most vertebrates the foramen is closed below by a basi- 

 occipital, above by a supraoccipital, bone.) 



The dorsal surface of the cranium is formed of a pair of 

 fronto-parietals behind, and in front of them an unpaired 

 sphenethmoid bone. Next come a pair of nasal bones, 

 their major axes transverse to that of the skull. In front 



