42 



ANATOMY AND PHYSIOLOGY OP 



OS SACRUM. 



Q. What is the popular name of this 

 bone ? — A. It is called the " r7(mp bone.'''' 



Q. Where is it located? — A. At the 

 superior part of the pelvis, between the ossa 

 illia. 



Q. What is the popular name of the 

 ossa illia ? — A. They are called the haunch 

 bones. 



Q. How many pieces enter into the com- 

 position of the sacral bone, in the foal? — 

 A. It is composed of five pieces. 



Q. How are they united ? — A. By fibro- 

 cartilaginous substance. 



Q. What ultimate change takes place in 

 this substance? — A. It becomes ossified, 

 and hence the solid bone. 



Q. How is the sacral bone divided ? — A 

 Into three surfaces, two borders, base, and 

 apex. 



Q. Describe its surfaces. — A. They are 

 named superior, inferior, and lateral. The 

 superior is convex, very irregular; on its 

 central line are five eminences, and laterally 

 are superficial grooves pierced by the four 

 sacral foraminte. The inferior surface is 

 smooth and slightly concave. The lateral 

 surface is thick anteriorly, gradually tapering 

 posteriorly ; they arc roughened for the re- 

 ception of the sacro-iliac hgament. 



Q. Describe, briefly, the base and apex. 

 — A. The base is composed of a central and 

 two lateral parts. The apex is oval, and 

 articulates with the anterior bones of the tail. 



BONES OF THE TAIL (oSSA COCCYGIs). 



Q. What is the situation of the ossa 

 coccygis ? — A. Posterior to the sacrum. 



Q. Of how many bones is the tail com- 

 posed ? — A. Fifteen. 



PELVIS OR HAUNCH BONES (oSSA INNOMINATa). 



Q. How do anatomists divide these 

 bones, in the foetal state ? — A. Into ilium, 

 ischium, and pubes. 



Q. In the adult horse are there more 

 than two bones ? — A. They are considered 

 as two, yet in reality they are united at the 

 pubes so as to constitute but one bone. In 



this state, however, they are denominated 

 ossa innominata — unnamed bones. 



Q. What is the situation of the iliatic, 

 ischiatic, and pubic portions? — A. They 

 are in the anterior, superior, and lateral parts 

 of the pelvic region. The ischiatic extends 

 posteriorly and the pubic inferiorly. 



Q. What are the connections of the 

 ossa innominata? — A. They are connected, 

 anteriorly and inferiorly, to the os sacrum ; 

 posteriorly and inferiorly, to each other, 

 forming the symphysis pubis ; laterally, 

 with the thigh bones. * 



Q. What are the uses of the pelvis? — 

 A. It affords an arch for supporting the 

 posterior parts. It contains the urinary or- 

 gans, rectum, etc., gives protection to blood- 

 vessels and nerves, and origin and insertion 

 to various muscles and ligaments. 



CHEST OR THORAX. 



The thorax or chest is formed by the 

 dorsal vertebrae, superiorly ; ribs, laterally ; 

 arid sternum, inferiorly. It also affords pro- 

 tection to the principal organs of circula- 

 tion and respu'ation. 



Q. State the number of ribs and their 

 arrangement? — A. Their number is gener- 

 ally thirty-six ; eighteen on each side, eight 

 of which are termed true, and the remainder 

 false, ribs. 



Q. Why are the anterior eight called 

 true ribs ? — A. Because they have a direct 

 cartilaginous insertion into the breast bone 

 or sternum. 



Q. Why are the posterior ten termed 

 false ribs? — A. Because they are indi- 

 rectly connected with the sternum. 



Q. What is the general conformation 

 of a rib ? — A. It is lengthy, curved ; con- 

 vex outwardly or laterally ; terminating in 

 a sharp border posteriorly, which forms a 

 posterior convexity. On the inner surfaces 

 it is concave, and of course the reverse of 

 the external. 



Q. What are the variations in ribs ? — 

 A. They vary in length, degree of curva- 

 ture, and obliquity of direction. 



Q. How shall we divide each rib ? — A. 



