N o. 2.] HE A RT OF L l/NGLESS SA LA MA NDERS. 327 



sinus venosus is provided with muscular walls, whose contraction 

 marks the first stage of the heart-beat. The return of the 

 blood from the auricle into the sinus is prevented by a valvular 

 contrivance, which, according to Fritsch (11), corresponds to 

 the valvula Eustachii of higher vertebrates. 



The two auricles of Salamandra show externally no evidence 

 of separation. A furrow on the ventral auricular surface indi- 

 cates the position of the truncus arteriosus and does not corre- 

 spond to that of the septum, which lies farther to the left. An 

 examination of the interior of the heart shows that the septum 

 is somewhat oblique to a median vertical plane, the inclination 

 being from left above to right below. Dorsally it attaches close 

 to the edge of the sinus-atrium opening ; caudally it hangs with 

 a free margin over the atrio-ventricular opening. According 

 to Langerhans, the septum atriorum of Salamandra maculosa is 

 always perforated, particularly in its dorsal third. It is supplied 

 with an abundance of muscular tissue, which contracts with the 

 walls of the auricles. 



Of the three openings in the auricular walls, two are provided 

 with valves, the third is valveless. Of the former, the atrio- 

 ventricular opening is guarded by two fibrous pouches, whose 

 margins are connected by means of cords to the wall of the 

 ventricle. The anterior surface of each valve is attached at its 

 middle to the margin of the septum atriorum. Between the 

 two points of attachment the septum hangs free. 



The sinus-atrium opening lies in the dorsal wall of the right 

 auricle. The plane of the opening is almost transverse to the 

 axis of the body, but its left margin lies usually somewhat 

 anterior to the right. Immediately in front of the opening we 

 find the pulmonary vein, which is formed on the dorsal side of 

 the heart by the union of two vessels, one from each lung. At 

 the dorsal margin of the sinus opening the vein penetrates the 

 atrial wall, on whose inner surface the now flattened vessel ex- 

 tends forward and toward the left, until, at the anterior margin 

 of the sinus-atrium valve, it reaches the septum, through which 

 it discharges into the left auricle. From the sinus opening to 

 the septum, the vein is closely united to the atrial wall ; the 

 latter, however, is dorsal to the vein, as is shown by the struc- 



