of Human Monstrosity. 227 



one fetus and the left of the other. These arteries present nearly 

 the usual subdivisions, the right carotid is the largest, has a much 

 more oblique course to the head than the other: it also gives oft" 

 the greater number of branches, the arteries of the thyroid in a 

 great measure coming from it alone. It divides as usual at the 

 angle of the jaw. The other carotid, also sends off a thyroid, facial, 

 internal maxillary, occipital, temporal, &c. but these are small 

 branches, and it principally goes to the brain as internal carotid. 



The aorta then arches gently downwards to the spine of the 

 fetus B. It then gives off" the left subclavian to this fetus next 

 the right, and from these the two vertebral arteries, &c. arise. It 

 finally terminates in the two umbilical arteries of this fetus after 

 supplying all the parts nearly in the usual manner. 



The veins which return the blood from these arteries have a 

 curious destination. The ascending cava enters the right auricle 

 of the other heart, and the azygos and right subclavian veins 

 join the descending cava of that heart also: whilst the veins ac- 

 companying the arteries which arise from the arch of the aorta, 

 and the left subclavian vein form the descending cava of the 

 same heart from whence those arteries arose. 



The arterial and venous systems of the other heart are exactly 

 similar to what has been described. So that the brain of one 

 fetus derives its internal carotid on one side and its two basilar 

 arteries from one heart, and the other internal carotid from the 

 other heart. It follows that the faces and eyes, moulded though 

 they be from corresponding parts of different fetuses, derive their 

 blood, nevertheless, from the same heart. 



The dura mater passing from the occiput and tentorium of one 

 fetus in the usual way, joins that coming similarly from the other, 

 to form a common falx. The cerebral lobes are moulded into 

 one mass on either side of the falx, and present no appearance 



F F 2 



