160 Dr. Clarke's Description of an extraordinary 
to observe, that the parts were examined too carefully for 
such a suspicion ; and, in the next, as there were no bones 
representing either the cranium, or spine, or os sacrum, it is 
not probable that their contents should exist in any other 
situation. 
Another objection may perhaps be taken from the anasto- 
mosis of the vessels of the monster, with those of the perfect 
foetus, and it may be assumed, that the nervous influence 
might be transmitted, in this way, along the vessels ; but 
there is very good reason for believing that the vessels of the 
placenta have no nerves, since, when we cut the navel-string, 
neither the mother, nor the child, expresses the smallest sign 
of sensation : and indeed', even if they had nerves, it is still 
very unlikely that, merely by such anastomosis, any nervous 
influence could be conveyed. 
I think it right to answer another possible objection which 
may be made, viz. that nervous matter may be co-extended, 
or co-existent with all other animal matter, and that, of 
course, it is of no consequence whether there be any sen- 
sorium, or reservoir of impressions, &c. or not ; because the 
stimulus, which produces action, must reside in parts, as well 
as the other substance of which they are composed. 
Now, although this may possibly be true, we have no evi- 
dence of the fact sufficiently satisfactory to carry conviction 
along with it. On the contrary, there seems to be good 
reason for entertaining an opinion, that nervous influence is 
conveyed from the brain downwards. If we are right in this 
conjecture, which is warranted by the experiment of tying, 
or cutting nerves, then the existence of the nervous fibre, 
like that of a string of a musical instrument, would be inactive. 
