384 



THE ANATOMY OF THE HORSE 



The inferior surface presents two slightly convex divisions, with a 

 prominent smooth ridge dividing them, running from behind forwards. 



The anterior surface presents superiorly a smooth triangular articula- 

 tory surface, and inferiorly a porous, roughened face. 



The posterior surface is triangular, roughened, and porous. The 

 extremities, the internal and external, turned upwards, terminate obtusely. 



THE PELVIS 



The general features belonging to the pelvis have been alluded to in 

 the last chapter, and the sacrum which forms its upper wall has been 

 described in this. It remains now to ascertain the shape and anatomical 



Fia. 32.— Pkoi-ile View of tiik two Ossa Insominata. 



1. 1. Wings of the iliac bones. 



2. 8. Pubic bone. 



3. Ischiac bone. 



4. 4. Superij-posterior spinous process of the two 



ossa ilii. 



5. An tero- inferior spinous process of the left ilir 



6. Tlie narrow part or neck of the ilium. 



7. 7. Obturator holes (foramina). 

 9. 9. Tuberosity of each ischium. 



10. Acetabulum. 



bearings of the bones which complete the arch. These in the embryo are 

 three on each side, uniting below in the median line by symphysis, and 

 above to the rough surface on the side of the sacrum. These three are 1st, 

 Os ischi ; 2nd, Os ilii, and 3rd, Os j^uhis. The whole bone, which is firmly 

 united in the adult, receives the somewhat paradoxical denomination of 

 Os innominatum, or the unnamed bone. 



On referring to the skeleton at page 348 it will be apparent that the 

 attachment of this bone to the sacrum is so arranged that it shall act as a 



