28 THE ARMY HORSE. 



Gluteus externus is a V-shaped muscle situated on the iipj)er 

 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 ujDper 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 ilimn and sacrum and is 

 inserted on the upper ajid 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 internus is situated underneath the gluteus maximus 

 and above the hij) 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^ hronchi, bronchial tubes, and air 

 cells. All of these organs, except the air cells, are lined with a 

 soft tissue called maicoiis Tnembrane; where organs open to the 

 external surface the mucous membrane and the skin are con- 

 tinuous. 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 turbinated hone into three pas- 

 sages, all lined with a delicate rose-colored mucous membrane, 

 called the &Ghneiderian memhrane^ which is continuous with 

 the skin of the nostrils. 



The 2)harynx 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 is a complex musculo-cartilaginous valve, situated 

 at the front part of the trachea or windpipe. It gives passage 

 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; it lies in the back part of the maxillary space and is 

 commonly known as "Adam's apple." 



The trachea^ or windpipe, is a cylindrical, flexible tube con- 

 sisting of a series of incomplete cartilaginous rings, numbering 



