VI 



.4 1! A < 'JIXOIDEA BLOOD-VASCULAR SYSTEM 



527 



cephalica. It is perhaps the remains of an originally long tubular 

 heart which reached as far as the anterior region of the body, and 

 which ceased to develop ostia. 



The heart lies in all Araehnoidea in the. abdomen, or in that part 

 of the body which corresponds with the abdomen. 



Scorpionidse (Fig. 370, A). The extended tubular heart of the Scorpion 

 lies in the pre-abdomen. It is 8 chambered, and has 8 pairs of lateral openings. 

 From the posterior end of each chamber a pair of lateral arteries diverges. The heart 

 is continued posteriorly into an aorta of the post-abdomen, and anteriorly into an 



A 



FIG. 370. The hearts of various Araeh- 

 noidea. A, Scorpion (after Newport). Ji, 

 Araneid. (.', Obisium silvaticum, juv. 

 (Pseuclosnorpionid) (after Winkler). 1>, 

 Gamasus fucorum, larva (after Winkler). 

 E, Young Phalangid (after Winkler). 



ad 



FIG. 371. Heart of a Spider (I'hokiis 

 )ilii'langoiih's) (after Schimkewitsch). ac, 

 Aorta cephalica; o, ostia of the heart ; r/<, 

 origin of the vena pulmonalis; i, a->, 0,3, 

 lateral arteries of the heart; on, aorta or 

 arten'a abdoininalis ; /, alary muscles, 

 attached to the pericardium ; j>r, pericardium. 



aorta cephalica which runs through the cepb.alo-th.orax. From the posterior aorta 

 several lateral pairs of arteries arise. Immediately in front of the most anterior pair 

 of ostia, and thus at the root of the aorta cephalica, a lateral artery is likewise given 

 off on each side. A little further forward there are two more lateral arteries running 

 downwards, and embracing the oesophagus, so forming an cesophageal ring. From this 

 cesophageal ring arises a medio-ventral longitudinal vessel running backwards ; this 

 lies above the ventral chord, and is called the supraneural vessel. In front of the 

 vessels forming the cesophageal ring the aorta cephalica gives off numerous other 

 arteries, principally to the 6 pairs of extremities. 



All the arteries apparently open into a lacunar system of the body, through which 

 the blood flows in special currents, those of the pre-abdomen bathing the book-leaf 



