352 



Georgina Sweet 



usual 3 arches, of which only the L. carotid and R. and L. 

 pulmo-cutaneous arches are normal. The right carotid arch, 

 after giving off the lingual artery, continues round as an 

 abnormally large vessel to empty into the right systemic arch 

 just where the latter gives off the occipital and subclavian 

 arteries, and two branches to the roof and sides of the oeso- 

 phagus. There is no branch corresponding in destination to 

 the ordinary carotid artery on this R. side. On the left side 

 the carotid arch is normal, but the left systemic arch ends 

 abruptly just after giving oft' the occipital and subclavian arteries. 



Thus Ave have here on the right side a disappearance of the 

 part of the right half of the dorsal aorta anterior to the 1st 

 branchial arch of the tadpole ; while the connection between 

 this arch and the 2nd arch, which usually persists as a solid, 

 connective-tissue thread, the ductus Eotalli, is here still widely open. 



On the left side, the part of the left half of the dorsal aorta 

 posterior to the origin of the subclavian artery has disappeared. 

 It is difficult to understand how the brain gets its normal 

 supply of blood, since the right carotid arterj'- is absent, and 

 no other vessel appe-ars to take its place, and the left carotid 

 artery is only normal in size and distribution. The arteries in 

 general appear less subject to variation than do the veins. It 

 may be noticed that occasionally the oesophageal arteries 

 leave the systemic arch behind instead of in front of the 

 subclavian arteries. 



fii). — Veins. 



These show a curious tendency to split into 2 branches, 

 reuniting a little distance on, thus forming a loop (see Text 

 figure .5) generally not surrounding any special structure. This 



Ahnorinalities in vfins belonging to the 

 prccaval systoni of Hyla aurea. 



A.V.C. Anterior Yeua Cava. 



/\\/C. 1^-T- Kxteniiil .lut>nlar Vein. 



I.J. Internal .lugular Vein. 



I. Innominate Vein. 



8^- Suliscapular Vein.- 



S" Subclavian Voin. 



F/o S 



