628 



BLOOD-VASCULAR SYSTEM OF THE HORSE 



heart, but is interrupted l)y the origin of the pulmonary artery. The longitudinal 

 or interventricular grooves, right and left (Sulci longitudinales sinister et tlexter), 

 correspond to the septum between the ventricles. The left groove is left-anterior 

 in position. It begins at the coronary groove behind the origin of the pulmonary 

 artery, and passes downward almost parallel to the posterior border, but does not 

 reach the apex. The right groove is right-posterior in position. It begins at the 

 coronary groove below the termination of the posterior vena cava and passes 

 downward and a little backward, ending about an inch and a half (ca. 3 to 4 cm.) 



"■->-, Right 

 atrium 

 {sinus 

 venosus) 



-''y^ Pulmonary veins 



Pulmonary 

 veins 



\ Posterior vena cava 



Left atrium {sinus venosus) 



Fig. 421. — Base op Hkart of Horse with Large Vessels, Dorsal View. Specimen Hardened in situ. 



above the apex. The grooves are occupied by the coronary vessel and a variable 

 quantity of fat. 



Size and Weight. — In horses of medium size the heart usually weighs about 

 seven or eight pounds (ca. 3.5 kg.), or about 0.7 per cent, of the bodj^-weight. 

 There is, however, great range of variation in apparently normal specimens. 



The following measurements were otitainetl in mediimi-sized hearts in diastole: 



Sagittal diameter of base 25 em. 



Greatest width of base 18 to 20 cm. 



Circumference at coronary groove 65 to 70 cm. 



Distance l^etween origin of pulmonary artery and apex 25 cm. 



Distance between termination of posterior vena cava and apex 18 to 20 cm. 



