THE RABBIT. 259 



is flattened and thickened at the margin, to form the 

 tuber osity of the ischium. The pubis is ventral. It is 

 separated in part from the ischium by the large, oval 

 obturator foramen ; but the ventral symphysis, uniting the 

 two halves of the pelvic girdle, is formed of both ischium 

 and pubis on each side, and the boundary line between 

 them is not discoverable except in very young speci- 

 mens. 



The bones of the hind limb are femur, tibia, fibula, tar- 

 sal, metatarsal, and phalanges, and a few small sesamoid 

 bones, developed in the tendons at some of the joints, 

 and not forming a part of the skeleton proper. The 

 largest of these sesamoid bones is the patella (or knee- 

 pan), developed in front of the knee joint in the tendon 

 of the extensor muscles of the leg. 



The femur is the single bone of the thigh. The large 

 bone of the shank is the tibia ; the small one, distinct at 

 its proximal end, but fused with the tibia distally, is the 

 fibula. The tarsus, like the carpus, consists of two trans- 

 ver^se rows of small bones, with a single bone between the 

 two rowso- The proximal row consists of two relatively 

 large bones, the distal row of three smaller ones, while 

 the single bone between the rows is at the inner side of 

 the foot. The metacarpals are a transverse series of four 

 elongated bones, and the phalanges are three in each digit. 

 The first digit of the foot, corresponding to the great toe, 

 is wanting. 



The rabbit is a representative of the vertebrate class 

 Mammalia (the mammals, or milk-givers). 



A cat or dog may well be studied, as showing the car- 

 nivorous type of mammalian structure ; and a bat, as 

 showing the adaptation of mammalian structure to aerial 

 locomotion. 



