SKELETON OF THE RABBIT. 555 



ventrally, but do not fuse in a symphysis ; the pubic sym- 

 physis is almost invariably present. Only in Cetacea and 

 Sirenia is the pelvis markedly rudimentary. 



The hind-leg consists of a thigh or femur, a lower leg with 

 two bones — the tibia and the fibula, an ankle or tarsus, the 

 sole bones or metatarsals, the toes with several joints or 

 phalanges. 



The head of the femur works in the acetabulum cf the pelvis. Near 

 the head are several processes or trochanters serving for the insertion of 

 muscles ; in the rabbit there are three, the great trochanter, the lesser 

 trochanter, and the third trochanter. 



In front of the knee there is a sesamoid bone — the knee-pan or 

 patella, and posteriorly there are smaller fabellis. 



In the lower leg, the tibia, which corresponds to the radius, is pre- 

 axial and in the normal position interior ; the fibula which corresponds 

 to the ulna, is postaxial and in the normal position exterior. In the 

 rabbit the fibula is slender, and is fused distally vrith the tibia. 



In the mammalian tarsus there are two rows of bones and a central 

 bone interposed between the two rows on the inner or tibial side. 

 Calcaneum Astralagus 



or Fibulare. (= Intermedium and Tibiale). 



Centrale 

 or Navicular. 

 Tarsale 5 and 4 Tarsale 3 Tarsale 2 Tarsale I 



=Cuboid. or or or 



External Middle Internal 



Cuneiform. Cuneiform. Cuneiform. 

 In the rabbit the first tarsal and the corresponding toe or hallux are 

 wanting. There are thus only four metatarsals and digits. Each 

 digit has four phalanges. 



Nervous System. — The brain has the usual five parts — 

 cerebral hemispheres, optic thalami, optic lobes, cerebellum, 

 and medulla oblongata, but the cerebral hemispheres cover 

 the next two parts, and the cerebellum conceals the medulla. 

 Of the brain-membranes, the dura mater lines the cranial 

 cavity, projecting longitudinally between the cerebral hemi- 

 spheres, and transversely between the latter and the cere- 

 bellum, while the vascular pia mater invests the brain closely. 

 There are the usual twelve pairs of cranial nerves. The 

 spinal cord gives off the usual spinal nerves, and there is a 

 sympathetic system as in most other Vertebrates. 



The cerebral hemispheres of the rabbit are but slightly convoluted, 

 and they leave the cerebellum quite uncovered. They are connected 

 transversely by a broad bridge — the corpus callosum, and beneath this 



