556 I'HILOSOPHICAL TRANSACTIONS. [aNNO 1748, 



have afforded, made him wish for a like opportunity, in some measure at least 

 to make amends for that fault. This opportunity presented itself in Jan. 1748, 

 not in a human fetus indeed, but in a calf, which the butchers of the hospital 

 cut out of a cow. The description of which monster is as follows. 



The integuments of the breast being raised, there appeared the union and reci- 

 procal insertion of the pectoral muscles of each subject into one common linea 

 alba. None but the inmost plans were attached to the bones. 



The muscles being removed, one sternum, common to both subjects, appeared 

 in sight. There was a sternum entirely similar to this, on the other or opposite 

 side. The heart was common to both. 



A trunk was formed by the reunion of the carotids, and the subclavians ; 

 which trunk commonly constitutes the superior aorta ; but in this subject it 

 only sends a small canalis arteriosus into the inferior aorta. There was a thick 

 common trunk of the pulmonary artery and the inferior aorta. The latter plainly 

 appears a continuation of this trunk; whereas it is commonly a continuation of 

 the aorta : and the pulmonary artery only furnishes the aorta, which makes but 

 one canal in ordinary subjects, with a canalis arteriosus, or canal of communica- 

 tion. And indeed he was of opinion, that this structure, which seems extraor- 

 dinary, is natural to every fetus that is not far advanced, as he explains it in his 

 course of physiology under the article of the fetus , and that it is a consequence 

 and proof of the mechanical and successive formation of the organs of its circula- 

 tion, which begins by the lower circle made by the umbilical vein, as the first 

 mover ; the trunk of the vena cava, the inferior aorta, and the branches of the 

 vena cava, which correspond with it. Now the one subject a had several marks, 

 which demonstrated that its formation was less advanced than that of the other 

 subject B. 



The umbilical vein of the subject b received a large branch of the umbilical 

 vein of the subject a: and which branch seemed to supply the place of the venal 

 duct that was wanting. Having thrown in the injection through this vein, the 

 heart and vessels of the 2 subjects were injected. 



The orifices of the umbilical arteries were but 2 in number, one for each 

 subject ; the one ahd the other issuing from the right iliac of each subject. 



The heart had only 2 cavities, as usual ; but the right cavity or ventricle be- 

 longed to the subject b ; and the left ventricle to the subject a. Into each of 

 the cavities there opened 4 orifices ; viz. two arterial, which were those of the 

 pulmonary arteries, and of the aortas ; and two venal orifices, or those of the 

 right and left auricles, for the blood of the cavse, and of the pulmonary veins. 



He gives the name of aorta to the superior arterial trunk of the subject a, in 

 conformity with the usual appellations, and because in common subjects this 



