^^FUNDAMENTAL CONSIDERATIONS 97 



Propelling Power. The propelling power of the horse is 

 in the hindquarters, the forelegs serving as a support or 

 balance to the body. Evidence of the location of the pro- 

 pelling power may be seen in an animal doing actual work. 

 Additional natural evidence is in the heavier muscling through 

 the coupling, loin, croup and quarters, as compared with other 

 regions. The energy is developed in the hindquarters, while 

 the strain of the propulsion comes in a large measure on the 

 coupling and loin muscles. A shallow flank is therefore in- 

 dicative of a general body weakness. If the power developed 

 cannot be borne by the correlated parts, additional or unusual 

 development in any special region is not of any distinct value. 

 That a chain is no stronger than its weakest link is evidenced 

 in the horse when placed in severe work or endurance trials. 

 The long, shallow body and loosely coupled animal cannot 

 endure severe strain, while the short, compact and deep- 

 muscled animal with a full, strong coupling can usually 

 continue in service indefinitely. The degree of power de- 

 velopment is dependent upon the formation of the bone, 

 and muscles, especially in the hindquarters. In the fore- 

 hand the shoulder blade does not form a direct attachment 

 with the mechanism proper, the horse having no collar bone. 

 The shoulder bone is sustained by the muscles which give 

 form or shape to the animal in this region. The difference 

 in the mechanism of the forehand and hindquarters is thus 

 indicative of the source of power and emphasizes the necessity 

 of full development in the latter region. 



EXPLANATION OF FIG. 17. 



I.H., atlas; 7.H., seventh cervical vertebra; I.R., first thoracic vertebra; 

 17. R., seventeenth thoracic vertebra; I.L., first lumbar vertebra; 6.L., 

 sixth lumbar vertebra; K, sacrum; I.S., first coccygeal vertebra; 16. S., 

 sixteenth coccygeal vertebra; 6.R., sixth rib; 6.K., costal cartilage; 18. R., 

 last rib; 1, scapula; I', cartilage of scapula; 2, spine of scapula; 4, humerus; 

 4', external epicondyle of humerus; 5, external tuberosity of humerus; 

 6, deltoid tuberosity; 7, shaft of ulna; 8, olecranon; 9, radius; 10, carpus; 

 11, accessory carpal bone; 12, metacarpus; 13, digit; 14, sternum; 14", 

 xiphoid cartilage; 15, ilium; 16, 16', external and internal angles of ilium; 

 17, ischium; 18, femur (shaft); 19, trochanter major; 27, trochanter minor; 

 28, trochanter tertius; 20, patella; 21, tibia (shaft); 21', external condyle of 

 tibia; 22, tarsus; 23, fibula; 24, tuber calcis; 25, metatarsus; 26, digit. 

 (After Ellenberger-Baum, Anat. f. Kunstler.) 



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