XIII 



PHYLUM CHORDATA 



285 



the systemic trunk in the form of a small connecting branch, 

 the ductus Botalli (d. lot.}. In the Anura, as we have seen (p. 261), 

 the third arch vanishes completely and there is no ductus Botalli. 

 As to the venous system, the Urodela exhibit very clearly the 

 transition from the Fish-type to the condition already described 

 in the Frog. The blood from the tail is brought back by a caudal 

 vein (Fig. 899, Gaud, v.) which, on reaching the coelome, divides into 

 two renal portal veins, one going to each kidney. From the kidney 

 the blood is taken, in the larva, into paired cardinal veins, each of 

 which joins with the corresponding jugular to form a precaval vein. 



_A c.arl 



e-ec.br.a 



\ct.ao 



FIG. 898. Heart and chief arteries of Salamandra. A, larva ; B, adult, of. br. a. 14, 

 afferent branchial arteries ; b. ao. bulbus aortse ; car. gl. carotid gland ; c. art. conus 

 arteriosus ; d. ao. dorsal aorta ; d. lot. ductus Botalli ; ex. br. 1 3, external gills ; ext. car. 

 external carotid ; int. car. internal carotid ; 1. au. left auricle ; Ing. lung ; pi. plexus, giving 

 rise to carotid gland ; pul. a. pulmonary artery ; r. au. right auricle ; v. ventricle. (Altered 

 from Boas.) 



In the adult the anterior portions of the cardinals undergo partial 

 atrophy, becoming reduced to two small azygos veins (card, post.) 

 which receive the blood from the region of the back : their posterior 

 portions unite and are continued forwards by a new unpaired vein, 

 the post-caval ( V. cava. inf.), which, joined by the hepatic veins, 

 pours its blood into the sinus venosus. The iliac vein from the 

 hind-leg divides into two branches : one joins the renal portal, 

 the other, representing the lateral vein of Elasmobranchs, unites 

 with its fellow in the middle ventral line to form the abdominal 

 vein (Aid. V.) and joins the hepatic portal, whence its blood, after 

 traversing the capillaries of the liver, is returned by the hepatic 

 vein into the post-caval. 



The red corpuscles are oval and nucleated, and are remarkable 

 for their unusual size. Those of Amphiuma are the largest 



