Cottrell. — Vascular System of Siphonaria obliquata. 



377 



sa 



A little before reaching this point the cephalic aorta gives rise to a 

 huge branch — the gastro-buccal artery (g.b.a.), which passes to the left 

 along the floor of the body-cavity, reaching the stomach on the ventral 



surface a little behind the point where 

 the oesophagus (fig. 2) enters. Here 

 it an once bifurcates, one branch — 

 the superior buccal artery (b.a.) — going- 

 forwards to the buccal mass, and the 

 other — the gastric artery {g.a.) — back- 

 wards along the ventral wall of the 

 stomach. 



The superior buccal artery passes 

 forwards as a large vessel along the 

 left latero-ventral side of the oeso- 

 phagus, and turns up with the latter 

 on to the dorsal surface of the buccal 

 mass, giving off small vessels to the 

 oesophagus on the way. On reaching 

 a point a little behind the buccal 

 ganglia it bifurcates into right and 

 left branches, A and B respectively 



Fig. 3. 



Arteries supplying the dorsal surface of 

 buccal mass ; / about 4. A, right 

 branch of buccal artery, which passes 

 below the oesophagus ; B, left branch 

 of buccal artery ; b.g., buccal ganglion : (fig. 3). Branch A passes under the 

 b.a., superior buccal artery ; r.s., end of oggopWus to the right side, and gives 

 ra dular sac : s.a., right salivary art erv ; ~. *, , • , i- ,-, 



s., salivary gland ; L, oesophagus. ' °$ *he artery which supplies the 



salivary gland. It then passes on to 



the latero-dorsal surface of the oesophagus and sends out a branch to the 



right buccal ganglion. These ganglia are well supplied with blood-vessels, 



and when the latter are well injected appear to be encased in an envelope 



of small arteries. An artery 



also runs on to the commis- 

 sure connecting these ganglia. 



Beyond this point branch A 



passes to the anterior end of 



oesophagus, and finally dips 



into the anterior muscles of 



the buccal mass. Branch B 



of the superior buccal artery 



has a similar distribution on 



the left side. 



Thus this branch of the 



gastro - buccal artery, which 



I have called the superior Arteries on the floor of the body supplying the head 



buccal, to distinguish it from 

 another vessel (the inferior 

 buccal artery), supplies the 

 oesophagus, salivary glands, 

 buccal ganglia, and some of 

 the dorsal muscles of the 

 buccal mass. 



and foot, as seen when the buccal mass is severed ; 

 X 2. A, B, and C, the three, main arteries supply- 

 ing the head ; B is the inferior buccal artery, and 

 is cut short ; cm., cephalic aorta (which is much 

 swollen at the point where it branches as it passes 

 between the pedal ganglia); g.b.a., gastro-buccal 

 artery; in., mouth (buccal mass being removed); 

 p.a., penial artery ; pd.a., pedal artery ; pd.g., 

 pedal ganglion. 



The gastric artery (fig. 2) 



a backward course on the ventral side of the stomach, giving off 

 branches to the ventral surface of the stomach ; the extreme posterior of 

 this organ, however, is supplied by a branch of the visceral aorta. 



