xii. iq CIRCULATION 337 



connected with regulation of the blood-pressure. However, it is 

 claimed that the first blood leaving as the ventricle contracts flows to 

 the lungs. In anurans this separation may be further assisted by an 

 arrangement such that the pulmonary arteries join at their base and 



V pulmon dext 



Vjug int 

 Vjug ext 

 v subscap 

 Vanonyma 

 — Vsubc/avia 

 V. brachlabs 

 V. cutan. magna 



V cava ant 



PuLmo dext. 



V bulb cord, post 



V cava post 



V dorso-lumb. 

 V. abdomen 

 Vjacobsonn 

 V oviduct- 

 Oviduct 

 V dxaca communis 



V 'renal reveh 



V hepat. (revehens) 



Intestlnum 



V porta e hepat 



Ovarium 



V.ovarica 



R.abdommaUs (VfemorJ 



V dica ext 



V ilica transversa 



V ischiadica 



V FemoraliS. 



Fig. 200. Diagram to show the chief veins of the frog. (After 



Gaupp.) The r. abdominalis is often called the pelvic and the 



v. iliaca communis the renal portal vein. 



open to the dorsal part of the truncus arteriosus (cavu'm pulmo- 

 cutaneum), which is partly separated from the more ventral cavum 

 aorticum, leading to the carotid and aortic arches. The classical view 

 of this system is that as the pressure rises the truncus contracts and 

 the spiral valve moves in such a way as to force all the blood that 

 leaves the ventricle during the later part of its contraction into the 

 ventral portion and hence to the systemic and carotid arches. In this 

 way a separation of blood from the right and left auricles would be 

 achieved. The view that the heart allows such a separation has, how- 

 ever, been challenged on the basis of experiments made by injection 



