xin 



PHYLUM CIIOTIDATA 



279 



een tlio gullet above and the epicoracoids 

 ual, of a visceral layer closely adiierent to 



8 1^ st.tr 

 pul.cuZr 



the coslomic cavity betw 

 below ; it consists, as us 

 the heart, and a loose 

 parietal layer, the two 

 being continuous at the 

 bases of the great ves- 

 sels and separated by a 

 small quantity of peri- 

 cardial Huid. 



The heart consists of 

 a sinus venosus (Figs. 

 929 and 933, 6-. v.), right 

 and left auricles {r.au., 

 I. mi.), a ventricle {v., ft.), 

 and a conus arteriosus 

 (r. art.). The sinus 

 venosus opens into the 

 right auricle, the pul- 

 monary veins into the 

 left: a striking advance 

 on the Dipnoi is seen 

 in the greatly increased 

 size of the left auricle 

 and its separation by 

 a complete partition, 

 the scptiim auriciUarum 

 (Fig. 931 .si')t.aur.),ivoxa 

 the right. The two 

 auricles open by a com- 

 mon auriculo-ventricular 

 aperture, guarded by a 

 pair of valves (cm. v. v.), 

 into the single ventricle. 

 The latter has a trans- 

 versely elongated cavity, 

 and its dorsal and ven- 

 tral walls are raised up 

 into muscular ridges or 

 trabecule with inter- 

 stices between them. 

 The conus springs from 

 the right side of the 

 base of the ventricle ; 

 it is separated from the 



latter by three small semilunar valves ('i^,), and is traversed 

 obliquely along its whole length by a large flap-like longitu- 

 dinal valve {l.v.) which springs from its dorsal wall and is free 



s 2 



Firi. 032.— Rana temporaria. The arterial system, 

 with the lieai-t, lungs, kidneys, and left testis, from 

 the ventral asi^eet. car. carotid artery ; car. gl. carotid 

 labyrinth ; c. art. conus arteriosus ; car. tr. carotid trunk ; 

 ctd. mes. cceliaco-mesenteric artery ; cu. cutaneous 

 artery ; d. ao. dorsal aorta ; du. duodenal artery ; gs. 

 gastric artery ; hp. hepatic artery ; it. iliac artery ; 

 ■int. intestinal arteries ; Ld. kidney; /. an. left amide ; 

 l(/. lingual artery ; In;/, lung ; &.<. (t^sojihagcal artery ; 

 pul. pulmonary artery ; pul. cu. tr. pulmo-cutaneous 

 trunk ; r. au. right auricle ; rn. renal arteries ; scl. 

 subclavian artery ; .rpl. splenic artei-y ; si/st. tr. systemic 

 trunk ; .ymi. spermatic artery ; ta. testis ; v. ventricle ; 

 rert, vertebral artery. 



