252 



The perineal glands are along the sides of the penis ; 

 their ducts open on small hairless patches, one at each side 

 of the anus. The secretion gives the rabbit a characteristic 

 odour. 



The panniculus adiposus is a layer of fat between the skin 

 and the underlying muscles ; beneath it is the panniculus 

 carnosus, a thin sheet of muscle, its contractions produce 

 twitching of the skin. 



Describe the Vertebral Column and Ribs of the Rabbit. 



There are seven cervical vertebrae. The first, the atlas, 

 is without a distinct centrum, has conspicuously broad 

 transverse processes, and a large neural ring, which is 

 divided by a ligament into an upper neural canal and a 

 lower space for the odontoid process of the second vertebra. 

 There is a slight neural spine ; and, in front, are the two 

 large articular concavities for the condyles of the skull. 

 The second, the axis, has small transverse processes. The 

 broad flattened centrum has large articular surfaces in 

 front, and beyond these it is produced as the odontoid 

 process (probably representing the centrum of the atlas). 

 The neural spine forms a large crest, bifid behind. The 

 remaining cervical vertebrae have the same parts as those 

 of birds ; the centra are short, and the spinous processes 

 are small. 



The thoracic vertebrae (12 or 13) have short thick centra, 

 short transverse processes, long neural spines, and bear 

 long curved movable ribs. Each of the first nine pairs of 

 ribs has two articulating heads (capitulum and tubercle), 

 the others have a capitulum only ; and only the first seven 

 pairs have their sternal portions (partly cartilaginous) con- 

 nected with the sternum. 



The lumbar vertebrae (6 or 7), the largest, have long 

 centra, prominent articular processes, crested neural spines, 

 and long transverse processes which are directed forwards 

 and downwards and expanded at their ends. 



The sacral vertebrae (2) are ankylosed to form the com- 

 posite sacrum for supporting the pelvis. 



The caudal vertebrae become reduced (size and processes) 

 towards the tip of the tail. 



Between the centra, which have thin epiphyses at their 

 ends, there are cartilaginous intervertebral discs. 



Give a Description of the Skull of the Rabbit. 



The chondrocranium is almost wholly replaced by bone ; 

 and the skull consists of replacement bones with additional 

 rnembrane bone,s (in italics). 



