EFFECT OF POISONING THE FOETUS. 
441 
only experiments in reference to this point with which I am 
acquainted were attended by a negative result. 
In his “ Compendium of Physiology,” Magendie briefly 
says, {( I have often injected very active poisons into the 
vessels of the cord, directing them towards the placenta ; 
but I have never seen the mother suffer from the effects of 
them.” 
And this negative result may be supposed to depend upon 
the fact that after all the communication between the 
maternal and foetal blood is only an indirect one, and is 
therefore limited. It may reasonably be believed to be one 
office of the cells which intervene between the foetal and 
maternal vessels to regulate or control such transmission, to 
exercise a selecting influence on the materials absorbed, as 
some other cells in all probability do. It is commonly sup- 
posed that the office of these cells is solely connected with 
the transmission of materials from the mother to the foetus, 
one set selecting and separating, and the other elaborating 
and absorbing them.* Therefore, even if an interchange to 
a certain extent be admitted, there is still no proof that 
poisons or other morbid materials, whether arising from 
within or from without, must necessarily pass from the foetus 
to the mother. 
But in whatever way the argument may be supported, it 
is certain that two very opposite opinions are expressed by 
physiologists on the subject. Dr. Harvey, after quoting 
this sentence from Mr. M‘Gillivray, u I am quite aware that 
many physiologists maintain that, in the highest species of 
animals, the blood cannot be returned by the foetus to the 
mother during utero-gestation,” endorses it with the follow- 
ing statement : <c That this opinion is very generally held by 
physiologists in this country is quite certain. Dr. Alison, 
for instance, after observing (on the authority of Magendie 
and of Dr. David Williams, of Liverpool) that camphor and 
oil injected into the blood of pregnant animals are soon 
detected in the blood of the foetus : but that poison injected 
into the umbilical arteries, although mixing with the blood 
on its way from the foetus to the placenta, does not affect 
the mother; and that fatal hemorrhage in the mother does 
not apparently diminish the fulness of the vessels of the 
foetus — adds ‘ so that it would seem that the transmission of 
fluids is almost entirely from the mother to the foetus.’ 
Again, Dr. Kirkes, referring to Professor Goodsir’s observa- 
tions as to the intervention of two distinct layers of cells 
* Kirkes’ ‘Physiology,’ 3d edition, p. 681. Carpenter’s ‘Manual of 
Physiology,’ 3d edition, pp. 151-5 and 526. 
