528 



BLOOD-VASCULAR SYSTEM OF THE HORSE 



heart, but is interrupted by the origin of the puhnonary artery. The longitudinal 

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

 correspond to the s('])tuni 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 apox. The right groove is right-posterior in position. It begins at the 

 coronary groove l^elow 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.) 



atrium 

 {sinus 

 venosus) 



— '^'"P^ Puhnonary 



Pulmonary 

 veins 



Posterior vena cava 

 Left atrium {sinus venosus) 



Fiu. 421. — Bask ov Heakt of Horsic with Large Vksski.s, Dorsal View. Si'kci.men Hardener in situ. 



above the apex. The grooves arc occupied ])y the coronary vessel and a variable 

 quantity of fat. 



Size and Weight. — In horses of me(Hum size the heart usually weighs alwut 

 seven or eight j^ounds (ca. 3.5 kg.), or about 0.7 per cent, of the body-weight. 

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



The following moasurcmonts were olitaiiUMl in nuMlium-sizod hearts in diastole: 



Sagittal diameter of l)ase 25 cm. 



Greatest width of ba.sc 18 to 20 cm. 



Circumference at coronary groove 6.5 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. 



