26 THE ARMY HORSE IN ACCIDENT AND DISEASE. 



powerful!}^ into play in kicking or rearing; it elevates the hind or fore 

 quarters, according as the fore or hind limbs are on the ground. 

 Acting on one side only, it bends the back and loins laterally. 



Gluteus extemus is a V-shaped muscle situated on the upper 

 and outer part of the haunch. It originates on the front part 

 of the ilium and at the second and third sacral spines. Inser- 

 tion, to the upper and outer part of the femur. Action, to draw 

 the thigh outward. 



Gluteus maximus is a very large muscle, originating in the lumbar 

 region; it is attached to the ilium and sacrum and is inserted en 

 the upper and outer portion of the femur. Action, to extend the 

 femur on the pelvis, and when the posterior limbs are fixed, to 

 assist in rearing. 



Gluteus intemus is situated underneath the gluteus maximus 

 and above the hip joint. It originates from the shaft (lower 

 angle) of the ilium and is inserted by a tendon to the upper part 

 of the femur. Action, to draw the leg outward and rotate it 

 inward. 



THE RESPIRATORY SYSTEM. 



(Plate V.) 



The organs of respiration are the nostrils, nasal chambers, 

 'pharynx, larynx, trachea, bronchi, bronchial tubes, and air cells. 

 AH of these organs, except the air cells, are lined with a soft tissue 

 called mucous membrane; where organs open to the external surface 

 the mucous membrane and the skin are continuous. The nostrils 

 are two oblong openings (right and left) situated in the front part 

 of the muzzle. The nasal chambers extend from the nostrils to the 

 pharynx and are separated from each other by the cartilaginous 

 septum nasi; each chamber is divided by the turbimded bone into 

 three passages, all lined with a delicate rose-colored mucous 

 membrane, called the Schneiderian membrane, which is continuous 

 with the skin of the nostrils. 



The pharynx is a muscular, membranous cavity, common to 

 the digestive and respiratory canals, somewhat cylindrical in form, 

 and extending back to the larynx and the esophagus. 



The larynx (commonly known as "Adam's apple") is a complex 

 musculo-cartilaginous box, situated in the back part of the maxillary 

 space, and at the front part of the trachea or windpipe. It gives pas- 

 sage to air and at the same time is the organ of voice. The front 

 extremity opens into the pharynx and the posterior into the trachea; 

 the front opening is guarded by a valve called the epiglottis or " pot- 

 lid," which closes mechanically in the act of swallowing and thus 

 prevents the passage of food or water into the trachea and lungs. 



