110 



VERTEBRATE RESPIRATION 



of the morphological relationships of these streams and the exits 

 of the arches at the anterior end of the conus. The precise nature 

 of the separation achieved by these mechanisms varies in the 

 species that have been examined so far. For example, in Xenopus 



* L. carotid 

 ■^L. systemic 

 L. pulmonary 



Blood from lungs 

 entering L. auricle 

 V 



Blood from 

 right side 

 of ventricle 



IS. VENTRICLE 



Fig. 32. 



The path of the blood in the conus of Rana as indicated by the 

 injection of very small quantities of Evans blue, (b) Superimposed 

 pressures recorded from two arches in a toad (modified after Simons, 

 1959.) 



the right auricle blood only goes to the pulmo-cutaneous arch 

 whereas in Rana and Bufo it mainly goes by this route but 

 some also enters the left systemic arch. Furthermore, blood 

 from the left auricle enters all three arches in Xenopus^ but in 



