112 THE SKELETON OF THE HORSE 



24 cm.) in the mare, 7J-2 inches (ca. 18.75 cm.) in the stallion. The transverse 

 diameter of the inlet is about the same as the conjugate in the mare, but is about 

 8 inches (ca. 20 cm.) in the stallion. The obliquity of the inlet or inclination of the 

 pelvis (Inclinatio pelvis) is greater in the female; the difference is indicated by the 

 fact that a vertical plane from the pecten cuts the fourth sacral segment in the fe- 

 male, the second in the male. The outlet is also larger in the mare, the ischial arch 

 being about one-third wider than in the stallion. The cavity is much more roomy 

 in the female; the transverse diameter between the middles of the superior ischiatic 

 spines is about 8 inches (20 cm.) in the mare, 6 inches (15 cm.) in the stallion. The 

 pubic part of the floor in the female is concave and lies considerably lower than the 

 ischiatic part, which is wide and almost fiat. In the stallion the pubis is very thick 

 medially, and this part of the floor is convex, while the ischial part is relatively nar- 

 row, and is concave from side to side. The obturator foramina are correspondingly 

 larger in the female. The ilium is shorter, especially with regard to its shaft, and 

 the greater sciatic notch is deeper and narrower in the male. The pelvis of the geld- 

 ing, when castration has been performed early, resembles that of the mare; other- 

 wise the male characters appear to be retained to a large degree. 



THE FEMUR 



The femur or thigh bone (Os femoris) is the largest and most massive of the 

 long bones. It extends obliquely downward and forward, articulating with the 

 acetabuluhi above and the tibia and patella below. It presents for examination a 

 shaft and two extremities. 



The shaft (Corpus femoris) is in general cylindrical, but flattened behind, and 

 larger above than below. The anterior, medial, and lateral surfaces are continuous 

 and strongly convex from side to side; there is often a central vertical rough line 

 on the proximal part, but otherwise these surfaces are smooth. They are covered 

 by the quadriceps femoris muscle. The posterior surface is wide, flat, and smooth 

 in its proximal fourth. Distal to this part there is a rough elevation laterally for 

 the attachment of the femoral tendon of the biceps femoris, and a roagh line medi- 

 ally to which the quadratus femoris is attached. The middle third is narrower', 

 and is rough for the attachment of the adductor muscle. Just distal to this area 

 an oblique groove crosses the surface, indicating the position of the femoral vessels. 

 The medial border bears on its proximal part the trochanter minor, a thick rough 

 ridge, to which the ilio-psoas muscle is attached. From this a rough line curves 

 up to the front of the neck and indicates the posterior limit of the attachment of 

 the vastus medialis muscle. A narrow rough area about the middle of the border 

 gives attachment to the pectineus muscle, and the nutrient foramen is usually 

 found just in front of this mark. The medial supracondyloid crest (Crista supra- 

 condyloidea medialis) is situated below the groove for the femoral vessels, and gives 

 origin to the medial head of the gastrocnemius. The lateral border is prominent 

 in its upper part, and bears at the junction of its proximal and middle thirds the 

 trochanter tertius ;i this process is curved forward, and has a thick edge to which 

 the tendon of the superficial gluteus muscle is attached. At the distal part is the 

 supracondyloid fossa (Fossa supracondyloidea),^ in which the superficial digital 

 flexor arises; it is bounded laterally by a thick, rough margin, the lateral supra- 

 condyloid crest (Crista supracondyloidea lateralis), to which the lateral head of the 

 gastrocnemius muscle is attached. 



The proxunal extremity (Extremitas proximalis) is large and consists of the 

 head, neck, and trochanter major. The head (Caput femoris) is placed at the 

 medial side and is directed inward, upward, and somewhat forward. It is ap- 

 proximately hemispherical and articulates with the acetabulum. It is cut into 



1 Also termed the external trochanter. 2 ^]gQ termed the fossa plantaris. 



