CHAPTER XXVII. 

 BRIEF ANATOMICAL STUDY OF THE HORSE. 



In all animal life the cell is the structural and functional 

 unit. A tissue is a collection of similarly differentiated cells. 

 A number of tissues grouped together form an organ. The 

 body is an aggregation of organs. We feed a horse to produce 

 tissue and to produce energy. The systems of organs are seven 

 in number. They are (1) skeletal, (2) muscular, (3) digestive, 

 (4) respiratory, (5) genito-urinary, (6) nervous, and (7) integu- 

 mentary. 



Skeletal system. The skeletal system is important as it 

 largely determines the conformation of the horse. The skele- 

 ton of the horse is composed of a number of bony segments, 

 most of which exist in pairs. The divisions of the skeleton 

 are (1) head, (2) neck, (3) trunk, and (4) limbs. The head 

 consists of numerous bones, mostly flat, united by sutures which 

 gradually undergo obliteration with age. The lower jaws are 

 strong and in each jaw there are six molar teeth (24 in all). 

 Twelve of these are temporary three in each jaw, and known 

 as the 1st, 2nd, and 3rd molars, while the 4th, 5th, and 6th are 

 permanent. There are also six incisors in the upper and six 

 in the lower jaw, all of which are temporary and are entirely 

 replaced by the time the animal is 4^ years old. 



The vertebral column is a chain of 54 to 56 irregular bones 

 (vertebrae) extending from skull to end of tail. There are seven 

 cervical (neck) vertebrae, 18 dorsal (back), 6 lumbar (loin), 

 5 sacral (croup), and 18 or 20 caudal (tail) vertebrae. From 

 above, the spinal column exhibits a concave cervical curve, a 

 convex dorsal curve, a nearly straight lumbar region, and the 

 sacro-caudal curve is concave below. The 3rd, 4th, and 5th 

 dorsal vertebrae have the highest spines which form the withers. 



There are 18 pairs of ribs, 8 of which are true and 10 false. 

 The 8 true pairs join the 8 segments of the sternum or breast 

 bone. The 7th or 8th ribs are longest. There is no collar 

 bone (clavicle) as in man, and the fore limbs are not attached 

 to the trunk but are connected by intervening muscles. The 

 hind limbs are united to the trunk by the pelvic girdle which, 

 in reality, is composed of three segments on each side. 



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