Production of Human Generation, &c. 161 
unless it received an impression, which, with regard to the 
nerves, should come from the brain. 
The whole of the actions of this monster, then, must have 
been those of the vascular system entirely ; and these seem 
to have been capable of forming bone, skin, cellular substance, 
ligament, cartilage, intestines, &c. 
The defect of heart (not an uncommon kind of mon- 
strosity) proves, that the energy of the arteries was equal to 
carrying on the circulation, not only in its own body, but 
also through its own placenta. 
The deficiency of nerves renders it extremely probable that 
their use is very small, if any, to the embryo. 
It has been an opinion, entertained by a very acute physio- 
logist, Mr. John Hunter, that, in all cases, a foetus is a 
very simple animal, as to its internal actions, and the circum- 
stances attending this monster fully confirm his idea. 
The usual objects of nature in the formation of a foetus 
are, that it should grow, and that it should be fitted with 
parts which, though of no use to it then, are essential after- 
wards. We know that the lungs are of this kind, and it is 
very likely that the brain and nerves are so too.* 
The common uses of the nervous powers are, to convey im- 
pressions from without, and volition from within. Now a 
foetus in the uterus is exposed to no external impressions, and 
is most probably incapable of volition, since it is not con- 
* That there is a very material difference between the internal functions of a foetus 
in the womb, and those of an infant after birth, seems very presumable ; not only 
from finding that it can carry on life without parts which are of the greatest moment 
afterwards ; but also from its possessing parts which after birth go into decay, or dis- 
appear, as the thymus gland, &c. 
