40 PRINCIPLES OF VETERINARY SCIENCE 



The transverse processes are wide, flat plates, resembling an 

 undeveloped rib. 



The sacrum, or croup, is composed of five vertebral segments 

 which are fused so as to form a single bone. It is triangular in 

 form and is wedged between the ilia. Two surfaces, two borders, 

 a base, and an apex are presented for description. The dorsal 

 surface has a crest composed of the partially fused spinous proc- 

 esses. The ventral surface is slightly concave from before 

 backward. The borders are formed by the fusion of the trans- 

 verse processes and present in front a facet for the articular 

 surface of the ilium. The base is represented by the anterior 

 surface of the first sacral vertebra. The apex is small and articu- 

 lates with the first coccygeal vertebra. 



The coccygeal vertebrce comprise all of the movable vertebrae 

 behind the sacrum. They vary in number, depending on the 

 development of the tail, and gradually diminish in size, so that 

 the spinal canal finally becomes a mere groove on the upper 

 surface of the bones. 



The thorax, or chest, is made up of the ribs and the sternum. 

 It is much compressed laterally in its anterior part, but widens 

 behind. 



The ribs number eighteen pairs, and are connected at one 

 extremity with the thoracic vertebrae and at the other with the 

 sternum. They are divided into eight pairs of true ribs and ten 

 pairs of false ribs. The true ribs articulate directly by means of 

 their cartilages with the sternum, while the false ribs articulate 

 by cartilaginous extensions. A typical rib is an elongated flat 

 bone with two surfaces and two extremities. The external 

 surface is convex and roughened; the internal concave and 

 smooth. The dorsal end has three distinct parts, the head, 

 neck, and tubercle. The head is convex for articulation ith 

 the two dorsal vertebrae above it. The neck is the constricted 

 part below the head. The tubercle articulates with the trans- 

 verse process of the corresponding dorsal vertebra. The lower 

 end is enlarged and has a rough cavity for the costal cartilage. 

 The first rib is the shortest and is nearly straight, the others are 

 more or less curved. 



The sternum, or breast bone, is situated in the ventral part 

 of the chest wall. It is suspended by means of the ribs. There 

 are seven segments or sternebrse which never undergo complete 



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