62 VETERINARY STATE BOARD 



Name the muscles of respiration. 



Inspiratory : External and internal intercostals, levatores eosta- 

 rum, serratus antieus, serratus magnus, latissimus dorsi, diaphragm. 

 Expiratory: External and internal intercostals, serratus posti- 

 cus, triangularis stemi, great and small oblique muscles of the 

 abdomen, longissimus dorsi, and the retractor of the last rib. 



Describe the inguinal canal, stating the structures which it contains. 



A canal, two to two and one-half inches in length, on each side 

 and in front of the pubic bone, running downward, backward and 

 inward, comprised between Poupart's ligament of the great oblique 

 muscle, posteriorly, and the small oblique muscle anteriorly. Its 

 inferior orifice (external or cutaneous orifice, inguinal or external 

 abdominal ring) is much larger than the superior (internal) ring. 



The spermatic cord and vessels in the male, and the external 

 mammary vessels in the female pass through the inguinal canal. 



Describe the navicular sheath. 



The navicular sheath is a fibrous membrane which covers the os 

 naviculare and the single ligament of the pedal articulation. It is 

 reflected on the plantar aponeurosis of the flexor pedis tendon, in 

 front of this ligament and ascends to the inferior sac of the sesamoid 

 sheath, where it is reflected upon itself, thereby forming two culs-de- 

 sac, one superior and one inferior. It is lined by a synovial mem- 

 brane which aids the aponeurosis of the tendon in gliding over the 

 navicular bone. 



CtecuLATORY Organs 



State the position of the heart and show its relation to the right and 



left walls of the chest and to the sternum in the horse 



and dog. 



In the horse, the heart occupies a position in the middle line of 



the chest, corresponding to the third, fourth, fifth and sixth ribs, 



being enclosed in a sac and suspended from the spine by its aortic 



vessels. Its base is uppermost, its apex nearly touches the sternum 



but does not rest on the ribs. The diaphragm lies just behind the 



apex. The heart is separated from the right wall of the chest by 



the right lobe of the lung. There is a triangular notch in the left 



lung which exposes the left ventricle and allows it to make its 



impulse felt against the chest wall. 



In the dog, the heart occupies a more nearly median position, 

 resting almost entirely on the upper face of the sternum and about 

 equidistant from the right and left chest wall. 



