ANATOMY. 15 
sacrum and first two or three coccygeal vertebre; 
inferiorly, to the superior ischiatic spine and tuberosity 
of the ischium, | 
The Mare’s pelvis represents a somewhat cone- 
shaped cavity at the posterior part of the trunk 
continuing the abdominal cavity. It has an internal 
and an external surface, and two openings. 
The anterior opening is termed the inlet of the 
pelvis, by which the foetus enters the pelvic cavity. 
The posterior is known as the outlet or recto-urethral 
opening. 
’ Fie. 6. 
DIAGRAM OF THE Mare’s PELvic Axis. 
A, Inlet; B, Outlet. 
The diameters of the inlet are generally recognized 
as two: The supero-inferior or sacro-pubic, which is 
the width between the sacro-vertebral angle and the 
symphysis pubis. It varies with the size of the animal, 
but is usually between eight and ten inches. The 
transverse or bis-iliac diameter is the distance between 
one ilio-pectineal crest and the other. From seven to 
nine inches. 
