VASCULAR SYSTEM. 



283 



FlQ. 156. The conus of Salamandra 'macidosci laid 

 open (after Boas), showing the four rather ;long 

 semilunar valves of the anterior row, of which that 

 marked 1 is continued backwards as the longi- 

 tudinal valve (Sp). When only three valves j are 

 present, the valve marked 4 is absent. 



valves which guard the ventricular end of the conus and is continuous 

 with the convex posterior side of the right hand valve of the three (or 

 four) valves which guard its anterior end (Fig. 156). It is attached in the 

 main to the dorsal wall of the 

 conus and projects freely 

 into it, reaching half or two- 

 thirds of the way across it. 

 Its line of attachment lies in 

 the axis of the spiral into 

 which the conus is twisted. 

 In Salamandra (Fig. 157) the 

 branches of the ventral aorta, 

 which are continued as the 

 arterial arches, are connected 

 by a common sheath and are 

 given off as explained in the 

 following description. The 

 ventral aorta is undivided 

 posteriorly (Fig. 157), but in 

 front it is divided by a hori- 

 zontal septum into two com- 

 partments of which the ventral is again divided by three vertical partitions, 

 which do not however reach the hind end of the horizontal septum, into 

 four canals. Of these the two median are continued into the anterior 

 (carotid) arches (/). and the lateral into the second (aortic) arches (//). 

 The dorsal division is divided by a vertical septum into two, each of which 



is continued as the 

 at first >, conj oined 

 third and fourth 

 arches (IV). 



In Rana and [its 

 allies the conus has 

 three semilunar 

 valves at each end. 

 The -j -, longitudinal 

 valve " (Fig. 158) 

 begins on the ven- 

 tral side of the ven- 

 tricular ope n i n g 

 near the right 

 semilunar valve ; 

 its line of attach- 

 ment, running 

 across the ventral 

 side of the conus, 

 passes on to : its 

 left wall and then 

 on to the dorsal 

 wall, ending in front 

 in the right hand 



valve (No. 1 ; of the anterior row as described for Salamandra. It incom- 

 pletely divides the conus into two chambers, of which the right hand 

 one is called the cavum aorticum (Fig. 159), the other the cavum 



FIG. 157. Conus and ventral aorta of Salamandra maculosa ; a 

 piece of the ventral wall has been removed (after Boas). The 

 ventral aorta is slightly diagrammatic. I, II, IV. divisions of 

 the ventral aorta or roots of the arterial arches, I, the carotid, 

 //, the systemic, IV, the conjoined third and fourth (pul- 

 monary), pp, a bristle inserted into IV ; ct, limit between the 

 conus and ventral aotra (points a little too high up) ; 2, 3, 4, 

 three valves of the distal row corresponding to those similarly 

 numbered in Fig. 156 ; sp, longitudinal valve ; vd, vd", vd' valves 

 of posterior row. 



