SPECIAL CLINICAL EXAMINATION. 81 



OX and becomes apparent in other animals when the above 

 cited condition prevails, induced by a morbid congestion of 

 the blood at the heart. In the horse the venous pulse is seen 

 near the aperture of the thorax (lower portion of the neck). 

 A true (positive) venous pulse is pathological. It is 

 coincident with the heart's systole, and is produced by a de- 

 fective closing of the auriculo-ventricular valves, the blood, re- 

 gurgitating into the auricle. True venous pulse is 

 a characteristic symptom of tricuspid in- 

 sufficiency. 



Fig. 26. 



-VWVWv 



Venous Pulse— Horse. 



The valves in the jugulars do hot prevent the flowing 

 back of the blood, as they are commonly not well developed, 

 and if the vein be greatly distended they cannot close the 

 lumen of the vessel. 



III. The Heart. 



The heart is examined by palpation, percussion 

 and auscultation. 



Anatomical. In all domestic animals the heart lies in the ven- 

 tral portion of the thoracic cavity between the third and sixth 

 ribs, in the dog extending to the seventh rib. The great mass 

 of the organ (3-5) lies to the left of the median line, so that it 

 approaches nearer the left thoracic wall than the right one. It 

 does not occupy a perpendicular position, but an oblique one 

 directed from the right, in front and above to the left, backward 

 and downward, the left side of the apex reaching the chest wall. 



Horse. The base of the heart lies below the upper half of 

 the height of the chest cavity, resting against the thoracic wall 

 between the 4th and 5th intercostal space. The point of contact 

 occupies a surface of about 10 cm high and 6-8 cm broad. (Sec- 

 Fig. 27, page 87). 



Ox and small ruminants. The heart is smaller and 

 does not extend quite as far back as the 6th rib, its base, however, 

 extends to the median line of the chest. Between the 4th and 5th 



