THE BONES OF THE PELVIC LIMB 31 
hip bone), which joins its fellow of the opposite side ventrally at the symphysis 
pelvis, and articulates very firmly with the sacrum dorsally. The two coxal bones, 
together with the sacrum and the first three or more coccygeal vertebre, constitute 
the bony pelvis. The os cox consists originally of three flat bones, the ilium, 
ischium, and pubis, which meet at the acetabulum, a large cotyloid cavity with 
which the head of the femur articulates. These three parts are fused before growth 
is complete, but are considered separately for convenience of description. The 
ilium (Os ilium) is situated in the lateral wall of the pelvis, the pubis (Os pubis) in 
the anterior part, and the ischium (Os ischii) in the posterior part of the ventral 
wall. 
The thigh (Femur), like the arm, contains a single long bone, the femur (or 
thigh bone) (Os femoris). This articulates with the acetabulum above and the 
tibia and patella below. 
The skeleton of the leg (Crus) comprises three bones (Ossa cruris), viz., the 
tibia, fibula, and patella. The tibia is a large, prismatic long bone which supports 
the weight, and articulates distally with the tibial tarsal bone. The fibula is 
situated along the lateral border of the tibia, from which it is separated by the 
interosseous space of the leg. It is much more slender than the tibia and does not 
articulate with the femur. In the pig and dog it has a complete shaft and two 
extremities, but in the horse and ox it is much reduced and otherwise modified. 
The patella (or ‘““knee-cap’’) is a short bone which articulates with the trochlea of 
the distal end of the femur; it is to be regarded as a large sesamoid bone intercalated 
in the tendon of the quadriceps femoris muscle. 
The tarsus (or “hock’’) consists of a group of short bones, the ossa tarsi, 
numbering five to seven in the different animals. The proximal or crural row con- 
sists of two bones, the tibial and fibular tarsals; the former is situated at the tibial 
side, and has a trochlea for articulation with the distal end of the tibia; the latter, 
situated at the fibular side, has a process, the tuber calcis, which projects upward 
and backward and constitutes a lever for the muscles which extend the hock joint. 
The distal or metatarsal row consists of four bones when seven tarsal elements are 
present, asin the pig and dog. They are best designated numerically as first tarsal, 
second tarsal, etc. The central tarsal is interposed between the rows. 
The preceding terms are anglicized abbreviations of those introduced by Gegenbaur into 
comparative anatomy. The Latin names and synonyms are given in the following table: 
siprali(Ositarsi tibiale) Tt.) 2.2252... 2h cad Astragalus or Talus 
Fibular (Os tarsi fibulare, Tf.).............. ...Caleaneus or Os calcis 
Central (Os tarsi centrale, Tc.)...........:....- Scaphoid or Navicular 
First Tarsal (Os tarsale primum, T1l)............ First or internal cuneiform 
Second Tarsal (Os tarsale secundum, T2)........Second or middle cuneiform 
Third Tarsal (Os tarsale tertium, T3)........... Third or external cuneiform 
Fourth Tarsal (Os tarsale quartum, T4).. . ...Cuboid 
The metatarsal and digital bones resemble in general those of the corresponding 
regions of the thoracic limb; the differential features will be noted in the special 
descriptions. 
