CHAP. II. BONES OF THE HORSE'S LIMBS. 401 



between the acetabulum and the symphysis pubis is greater than in the 

 horse. 



To the head of the femur, or thighbone, is attached the round liga- 

 ment (lig amentum teres), which helps to fasten it in the acetabulum. 

 The lower end of the femur is furnished with a pulley-like surface, 

 or trochlea, on which the patella, or knee-cap, glides. 



The leg comprises three bones, the tibia, the fibula, and the patella ; 

 the first-named being by far the largest. The tibia is a long prismatic 

 bone, much thicker at its upper end. It extends downwards and 

 backwards, articulating with the femur above and with the astragalus 

 below, the latter by means of a perfect hinge-joint. The fibula is a 

 slender elongated bone, on the outer side of the tibia, and extending 

 about halfway or two-thirds along the latter. The patella is a small, 

 very compact, "floating" bone, attached to the tibia by three strong 

 ligaments. 



The region immediately below the tibia is known as the tarsus or 

 hock. It contains six bones, called tarsals. In the upper row are 

 two, the calcaneum, os calcis, or heel bone, on the outer side, and the 

 astragalus on the inner side. In the inferior row, beneath the 

 calcaneum, is the cuboid, whilst beneath the astragalus is the true 

 navicular, and beneath that a couple of cuneiform bones side by side 

 (see diagram on page 411). 



The astragalus is an irregularly cubical bone, its articulating surface 

 forming the most perfect pulley or trochlea in the body. The calcaneum 

 is a vertical elongated bone, flattened on both sides. The cuboid is 

 small and elongated. The navicular and the cuneiform bone next the 

 cuboid are very broad flat bones, much resembling each other in shape, 

 though the navicular is the larger. 



The metatarsal and digital regions in the hind limb are an exact 

 counterpart of the metacarpal and digital regions in the fore limb the 

 cannon bone with its splints on either side, and the single middle digit 

 made up of pastern, coronet, and coffin bones. 



Because the horse has one finger on each hand (fore limb), and one 

 toe on each foot (hind limb), he is called a monodactyje animal. The 

 ox and sheep (two-toed), are bidactyle : the pig (four-toed), is tetra- 

 dactyle. Man is pentadactyle, so is the elephant. 



An homologous relationship between the fore limbs and the hind 

 limbs is obvious. The corresponding parts are indicated in the 

 subjoined table : 



FORE LIMB. HIND LIMB. 



Shoulder Girdle, formed of the two Hip Girdle, formed of the two ossa 



scapulse. innominata. 



Humerus . Femur. 



f Radius 

 \ Ulna 



Carpals 



Metacarpal region 



Tibia. 

 Fibula. 

 Tarsals. 

 Metatarsal region 



(Cannon bone). (Cannon bone). 



Digital region Digital region 



(Pastern, coronet, and coffin bone). (Pastern, coronet, and coffin bone). 



D D 



