404 



COMPARATIVE ANATOMY 



Neither in Vrodela nor Anura is there a .septum ventriculorum, 

 so that the blood passing out from the spongy ventricle must have a 

 mixed character (Fig. 306). The ventricle is usually short and 

 compressed, but is more elongated in Amphiuma, Proteus, and the 

 Gymnophiona. It is continued anteriorly into a conus arteriosus; 

 this has usually a slight spiral t \vist, and possesses a transverse 

 row of valves at either end, as well as a spiral fold, formed by a 

 fusion of valves and extending into its lumen, thus partially 

 dividing it into a dorsal caw.m pidmoncde, and a ventral caw in 

 aortictim communicating with the carotid and systemic 



/. ft. 



y.a 



j. a 



Try/. 



FIG. 307. HEART OF Cryptdbranchiis japonicus. From the ventral side, i After 

 Rose.) The left atrium is cut open. 



L.i, L.i- 1 , the t\vo pulmonary veins, opening by a single aperture into the left 

 atrium ; L. Vh, P. Vh, left and right atria ; O.ar, atrio-ventricular aperture ; 

 P.d and P.*, left and right pulmonaiy arteries ; 8.n, septum atriorum, 

 perforated by numerous small apertures; tr, truncus arteriosus; V.c.d 

 r.t.x, posterior cardinal veins; r.* 1 . /, postcaval vein; V.j.d and !"../., 

 jugular veins; V.*.d and !".>.>-, subclavian veins; 1", 4", the four arterial 

 arches. 



arches. This holds' good, e.g., for Amblystoma, Salamandra, 

 Amphiuma, and Siren. In others (e.g. Necturus, Proteus, 

 Gymnophiona), the conus is more elongated, and reduction is 

 seen in the disappearance of the spiral fold and the presence of 

 only a single row of valves. 



In Anura, the fold lying within the conus extends so far back 

 that no undivided portion of the cavity is left. The consequence 

 of this is that the blood passing into the hindermost pair of the 

 arterial arches that from which the pulmonary arteries arise is 

 mainly venous, while the others contain more or less mixed blood 



