THE RABBIT 3*9 



pubis. In the middle of the lateral surface of each innominate 

 bone is a circular depression, the acetabulum, in which the femur 

 articulates. A large hole, the obturator foramen, is present in the 

 ventral half of the bone. The innominate bone is formed by the 

 union of four bones : the ilium, which forms its dorsal portion, by 

 which it articulates with the sacrum; the ischium and pubis, 

 which form its ventral portion ; and the acetabular bone, a small 

 bone in the acetabulum. The pubis lies anteroventral to the is- 

 chium, the union of the two pubes forming the symphysis pubis. 

 The acetabular bone is present only in mammals, and is mor- 

 phologically the lower end of the ilium, which is separated from it. 



Exercise 41. Make a drawing of the lateral aspect of the innomi- 

 nate bone. 



The skeleton of the hind leg may be divided into a proximal, a 

 middle, and a distal division. The femur, or thigh bone, forms the 

 proximal division; it is a cylindrical bone, at the upper end of 

 which is the head, which articulates with the acetabulum. At the 

 side of the head, and forming the proximal end of the bone, is a 

 protuberance called the great trochanter; below the head, and 

 medial in position, is a protuberance called the lesser trochanter ; 

 and on the opposite side of the bone, and lateral in position, is the 

 large third trochanter. At its distal end the bone ends in two 

 projections, the condyles. On the anterior side of the distal end of 

 the femur is a small bone which develops in a tendon and forms 

 the kneepan; it is called the patella. 



The middle division of the leg is formed by the tibia and fibula, 

 which appear as a single bone, the fibula being fused with the tibia 

 and forming a delicate splint on the lateral surface of its proximal 

 end. The tibia is the longest bone in the rabbit's body. The 

 distal division is formed by the tarsus, or ankle, and the pes, or 

 foot. The tarsal bones are six in number, the largest of which are 

 the calcaneum, or heel bone, and the talus, or astragalus. The 

 calcaneum is the bone which projects back from the ankle; the 

 astragalus is the large bone which articulates with the tibia. 



The skeleton of the foot is composed of four metatarsal bones 

 (the first metatarsal being present, but vestigial) and four digits, 



