Elementary Anatomy of a Hound 37 



during hot weather, and this enables it to keep the 

 bodily temperature at its normal standard. 



Continuing the description of the respiratory 

 organs, we may say that the larynx guards the 

 entrance to the windpipe or trachea, as the glottis ^ 

 i.e., the opening into the larynx, is closed during the 

 act of swallowing by a lid-Hke structure called the 

 epiglottis. When a foreign particle gains entry to 

 the larynx the act of coughing is excited in order to 

 dislodge it from its injurious situation. The trachea 

 is composed of a number of cartilaginous rings 

 united to form a tube, elastic and resistant, the course 

 of which is in front of the gullet, and quite super- 

 ficial, especially in its upper portions, but dividing 

 at the entrance to the chest into the right and left 

 bronchial tubes, which again divide and subdivide. 

 The larynx is the organ of voice, and barking, with 

 its varied modifications, all originate in this organ. 

 Lymphatic glands (absorbents), the thyroid gland, 

 and thymus (in pup) are additional structures 

 associated with the respiratory organs. 



The thorax or chest cavity has its side walls formed 

 by the ribs and the intervening intercostal muscles, 

 the latter contracting and relaxing with each com- 

 plete respiration. 



The floor of the chest is mainly formed of the 

 sternum ; the base of the former is represented by the 

 midriff, and the front of the chest by the brisket. 



