132 
Mr . Gibson's Description of an 
there was only one pair of the phrenic nerves ; one nerve on 
the outside of each neck, which was distributed to the dia- 
phragm in the usual way. The other nerves from the spinal 
marrow were in like manner distributed, as if the body had 
had but one spine. Thus the nerves of the right arm and leg, 
were supplied by the right side of the right spinal marrow : 
those of the left arm and leg, by the left side of the left spinal 
marrow. 
These are all the circumstances connected with this curious 
foetus, which I think worthy your notice ; and, having already 
sufficiently trespassed upon your patience, I subscribe myself 
Your obliged Servant, 
B. GIBSON. 
Explanation of Plate III. 
Anterior View of the Heart and Arteries , removed from the Body. 
2 . The right ventricle of the heart, connected with the left 
head. 
2. The left ventricle. 
3. The right auricle. 
4. The left auricle. 
5. The pulmonary artery at its origin. 
6. The ductus arteriosus. 
7. The aorta, 
8. The trunk, from which the two external carotid arteries 
of the left head arose. 
