XII 



PHYLUM CHORDATA 



whole length by a large flap-like longitudinal valve (Lv.) 

 which springs from its dorsal wall and is free ventrally. The 

 conus passes without change of diameter into a bulbus aortce, 

 the two being separated by a semilunar valve and by the 



au-.v.v 



FIG. 236. Rana temporaria. The heart from the ventral aspect with the cavities 

 laid open. a. a', bristle in left carotid trunk ; au. v. v. auriculo-ventricular 

 valves ; b. b' . bristle in left systemic trunk ; c. c . bristle in left pulmo-cutaneous 

 trunk ; car. a. carotid artery ; car.gl. carotid plexus ; c. art. conus arteriosus ; 

 car. tr. carotid trunk ; /. au. left auricle ; Ig. a. lingual artery ; /. v. longitudinal 

 valve ; pul. ctt. tr. pulmo-cutaneous trunk ; p^tl. v. aperture of pulmonary veins ; 

 r. au. right auricle ; s. au. ap. sinu-auricular aperture ; spt. anr. septum auri- 

 cularum ; v. v '. valves ; vt. ventricle. 



free end of the longitudinal valve. The bulbus gives off 

 two branches, right and left, each of them divided by two 

 longitudinal partitions into three vessels, an inner or anterior 

 Man. Zool. E E 



