THE MUSCLES OF TflE IIOKSE. M-? 



B. Latlssltnus Dorsi arises from tlie fascia of the loins, and tlio superior 

 spinal ligament ; it is inserted into the inner side of the humerus ; it aids 

 in retracting the arm and bracing the muscles of the back. 



C Postea Spi'iuttus is attached to the whole surface of the posterior fossa 

 of the scapula ; it is inserted into the humerus a little behind the outer 

 tubercle, and also to the upper part of the ridge, on the upper and outer 

 part of this bone. It flexes the arm on the shoulder. 



D. Antea Sp'matus is attached superiorly to the surface of the anterior 

 fossa, and two-thirds of the anterior casta of the scapula, inferiorly to the 

 greater and lesser tubercle of the humerus. It straightens the humerus 

 on the scapula and throws the shoulder outwards, 



E. Teres Externus arises from a tubercle on the posterior angle of the 

 scapula, and is inserted mto the upper and outer surface of the humerus ; 

 it aids in flexing the shoulder on the arm. 



F. Scapulo Ulnar is arises from the upper part of the superior and pos- 

 terior angle of the scapula, inserted into the inner and upper part of the 

 ulna, which it flexes on the scapula, and draws the elbow inwards. 



G and H. Caput Magnum and Medium of the triceps extensor hrachii, 

 arises from the posterior margin of the scapula, from a ridge on its neck ; 

 from the outer side, and from the body of the humerus, and is inserted into 

 the olecranon or point of the elbow. It is of great use in draught, in 

 pushing the body against the collar, or in forcing the forelegs under the 

 body. 



1. Pectoralis Magntis arises from the fascia of the external oblique 

 muscles, the ensiform cartilage and from the three last bones of the 

 Bternum, and is inserted into the inferior part of the inner tubercle of the 

 humerus ; it aids the muscles of the haunch in the propulsion of the 

 trunk, and assists in respiration. 



K K K. Serratus Magnus arises from the four last cervical vertebrae, 

 from the whole length of the first four ribs, and from portions of the four 

 next ; it is inserted into the conca\'ity of the scajjula. It moves the 

 shoulders in progression, and when at rest enlarges the chest and assists 

 in laboured respiration. 



L L. Obliquus Externus Abdominis arises by fleshy digitations from the 

 fourteen posterior ribs, from two-thirds of the crest of the ilium, and its 

 anterior spinous process ; it passes over the lateral and inferior portions of 

 the belly to meet its fellow from the opposite side, and form the linea alba, 

 230steriorly, into the symphysis pubis ; it assists in expelling the feeces and 

 urine. 



M. Gluteus Maxhrvus arises from the crista and the dorsum of the ilium, 

 and from the sacro-sciatic ligament ; it is inserted into the great trochanter 

 and also along the body of the femur, as far as the small external tro- 

 chanter ; its use when the hindlegs are fixed, is in raising the anterior 

 part of the body ; when in action, it abducts and retracts the femur, and 

 is actively engaged in kicking. 



N. Gluteus Externus arises from the spines of the ilium and sacrum and 

 is inserted into the small trochanter of the femur and the fascia of the 

 thigh ; it advances the femiu*. 



0. Triceps Abductor Fenioris arises from the spines and transverse 

 processes of the sacrum — from the sacro-sciatic ligament, from the great 

 trochanter of the femur and the tuberosity of the ischium ; it is inserted 

 into the outer side of the patella and the superior portion of the tibia ; its 

 action is to steady the body, and to raise it when the feet are firmly fixed, 

 as in leaping ; it is a most important organ of progression, and is not 

 inactive in kicking. 



F. Biceps Rotator Tibialis arises from the last sacral and two fii-st 



