Mammalia. 



159 



in the next part of the limb. Examine the ligaments that hold 

 the adjoining ends of the bones together. Examine the 

 cartilage on the end of the bones. Between the ends of the 

 bones of the limbs, note a small quantity of slippery liquid, the 

 synovia. In cleaning the bones, notice the nerves and blood 

 tubes passing in and out of the holes along the sides of the 

 bones. 



Weigh a rabbit, freshly killed, but from which the blood has 

 not been removed. Thoroughly clean the skeleton, and when it 

 is dry, weigh it. What part of the whole weight of a rabbit is 

 the skeleton ? 



i % The skeleton consists of two parts, the axial part, made up 

 of the skull and spinal column, and the appendicular part, 

 consisting of the limbs and the bones supporting them. 



2. In the skull, the joints are called sutures. The bones 

 surrounding the brain constitute the cranial part ; those parts in 

 front make up the facial part. Note that the face is large, 

 compared to the cranium. How do these two parts compare in 

 the rabbit, dog, horse, frog, ape, and man ? Why so much 

 difference ? Note the cavities and apertures in the skull : the 

 brain cavity ; the opening (foramen magnum) through which the 

 spinal cord passes to join the brain ; the cavity, or orbit, of 

 the eye, with its holes for the optic nerve ; the nasal apertures at 

 the front of the snout ; the auditory apertures, or ear holes. On 

 each side of the foramen is a smooth, rounded elevation ; these 

 are the occipital condyles. See how they fit the first vertebra ; 

 what kind of a joint do they make ? Study again the way the 

 lower jaw joins the skull, and consider the motions that this joint 

 permits. Compare it with the corresponding joints in the 

 skulls of a cat, cow, and man. 



3. Make a more careful study of the teeth than before, as 

 they are now fully exposed. The front teeth are the incisors ; 

 what is their shape ? How many above ? How many below ? 

 Are they all alike ? How are they arranged ? Are they all 

 marked alike ? How do the upper and lower incisors meet, 



