418 PROCEEDINGS OF THE ACADEMY OF [May, 



A short distance cephalad to the muscular the external jugular 

 receives, on its mesial side, two or three branches from the trachea, 

 larynx, and oesophagus, tr. Anterior to these vessels the external 

 jugular is formed by the union of two chief veins, the lingual, 1, from 

 the ventro-lateral surface of the tongue, and the inferior dental, id, 

 from the mesial surface of the lower jaw. The connection of the 

 superior dental (extending along the bases of the maxillary teeth) 

 with the jugular could not be determined with certainty, hence 

 that vessel is not shown in the figure. The same is true of the 

 small veins in the region of the cranium. 



The Arterial System. 

 The Abdominal Aorta and its Branches. 



The right and left aortic arches, fig. 3, Ao.d, Ao.s, arising from 

 the heart in the manner already described, form a rather long loop 

 and approach each other in the middorsal line. Here they are 

 united by a short, wide connective in such a way that the left arch 

 seems continued into the coeliac arterj^ and the right into the dorsal 

 aorta proper. Each arch, anterior to the connective, gives off two 

 fairly large branches, oe, to the posterior region of the oesophagus. 



The cceliac arterj^ fig. 3, c, is the largest branch of the abdominal 

 aortic system. After giving off a couple of small branches, oe, to 

 the posterior region of the oesophagus, it gives off a large spleno- 

 intestinal artery, si, to the spleen and small intestine. 



The coeliac then breaks up into three arteries of about the same 

 size: the gastro-hepatico-intestinal, ghi, carrying blood to the stomach, 

 liver, and small intestine; the pancreo-intestinal, pi, leading to the 

 pancreas and small intestine; and the gastric, ga, to the greater 

 part of the stomach. 



From the dorsal aorta proper, da, which, as has been said, seems 

 to be the direct continuation of the right aortic arch, several arteries 

 are given off; these will be described as they occur in an anterio- 

 posterior direction. 



At about the point of union of the two aortic arches arises the 

 most anterior of seven or eight pairs of lumbar arteries, lu 1-7; 

 this first lumbar artery is continued cephalad for some distance as a 

 longitudinal trunk that gives off several lateral branches to the 

 walls of the thoracic region. The other six or seven lumbars are 

 distributed to the dorsal body wall, and arise, at more or less regular 

 intervals, as far caudad as the sacrum, or even back of that point. 



The first large branch of the aorta is the unpaired mesenteric 



