[ H ] 
cava fnf.erior, d. b. which rids by the *: vertebrae up 
to F. and into the cava inferior , d.g. i. It would 
be abfurd to place the only moving power of circu- 
lation in the vena- cava, or indeed in any vein. 
2. When you have placed it there, what will this 
fuppofition tend to ? 3. This vein fubdivides, and 
ramifies itfelf through the kidney-liver , the mufcles 
and the fpine ; but none of its branches communi- 
cates with the aorta. The aorta on its part fends 
feveral branches into the kidney liver , very (lender, 
and refembling, by their tranfverfal dire&ion, the 
common emulgents, but very different in (ize. If then 
the circulating force were placed at d. it could only 
produce an inverfe circulation, by the communica- 
tion the cava might have by its capillary branches, 
with the like ramifications of the aorta, which fup- 
pofition feems too much againff nature to counterba- 
lance the other opinion, which makes the trunk e. 
of the aorta , a portion of the umbilical vein, and 
the fubftitute of the heart. 
Another anatomical fadt proves this laft opinion ; 
which is, that the aorta, and efpecially the fuperior, 
F. ran up as high as the cranium , and was of a 
pretty coniiderable (ize, while the venal trunk, d. 
had nothing but capillary branches in the upper parts j 
fo that it almoft appeared evident that the veffel, e. F. 
was connected with the chief mover of the fluids. 
Wherefore, fuppofing the trunk, d. to be the vena 
porta , or an imperfect cava going to fome of the 
vifeera , being the rudiments of an imperfedt heart, or 
a vena-cava ending in a pouch, as the inteftines did 
which fhould have entered the ftomach, if there had 
been one; the difficulty almoft diiappears. I fay almoft, 
becaufe, even on this fuppofition, if there was a circula- 
