CHAPTER IV 



THE BONES— FRACTURES AND EXOSTOSES 



THE INNOMINATE BONE 



This is a bone which is very irregular in shape. It is made up of three 

 segments. These are named respectively the ilium, ischium, and pubis. 

 In the foetus these segments are separate, but in the adult animal they 

 become completely ossified to one another, so that it becomes impossible 

 to mark out the lines of division of the different bones. The two 

 innominate bones meet at the ischio-pubic symphysis where, in the 

 adult animal, they also are firmly ossified to one another. The bones 

 thus united form the floor and the osseous lateral boundaries of the 

 pelvic cavity. 



The three parts of the innominate bone meet one another in the 

 cotyloid cavity or acetabulum. This cavity is placed on the outer 

 aspect of the innominate bone, and it looks downwards and outwards. 

 The acetabulum is deep and cup-like. It is articular, but not entirely, 

 since it presents a triangular non-articular roughened area, the apex ot 

 which is placed near the centre of the cavity from whence the non- 

 articular area extends to the inner portion of the circumference. The 

 cotyloid cavity has a well-marked rim which gives attachment to the 

 cotyloid ligament. This ligament serves to deepen the cavity and thus 

 afford better accommodation for the articular head of the femur. 

 Inwardly the rim of the cavity is deeply notched along the base of 

 the triangular non-articular area mentioned above. The notch is 

 bridged over by a continuation of the cotyloid ligament, this particular 



