Here is what they were trying to determine:
The specific problems which we set out to investigate were:
(1) Would the offspring at birth be intermediate in size between the
normal offspring of the parent breeds? If this were to be so the foetus in
the small mother would certainly be too large and would either cause
death of the mother or very difficult parturition or possibly premature
abortion, while in the large mother the foal would be very much smaller
at birth than normal for the breed.
(2) Would, on the other hand, the size of the mother by virtue of the
growth-promoting substance available exert a controlling influence on the
size of the foetus, so that in the case of the small mother the foetus would be limited in growth to such a size as she would normally give birth to, while in the case of the large mother the foetus would develop up to thesize normal to the large mother?
(3) If a difference in size at birth were established, would this affect the
subsequent growth and permanent proportions of the body?
(4) If permanent differences in adult life were established, would these
differences be transmitted to subsequent generations?
Naturally a complete answer to the last question cannot be given for
several years but we now have evidence to present on the first three.
Here is a quick paragraph about foal size:
Weight of foals. It will be seen that the weights of the cross-bred foals
out of the Shetland dams are not significantly different from the weights of
pure Shetland foals. The weights of the reciprocal cross are smaller than
the weights of the pure Shire, but obviously there are not sufficient data to show whether this is significant, although it may be so. Of the pure Shires,one was small for the breed and the other large. Mr A. G. Holland,
Secretary of the Shire Horse Society, informs us that the weights of good
pure-bred Shire foals at birth are between 68 and 77 kg. (150 and 170 lb.).
It is obvious, however, that in each reciprocal cross there has been very
complete regulation of the size of the foal, the foals in the small mothers
being limited in size to that of Shetland offspring and those in the large
mother growing unchecked, although perhaps not quite reaching the full
size of a Shire foal. When the weights of the foals relative to the weights
of the dams are compared it will be seen that the percentage weights are
not significantly different, except possibly that the cross-breds from the
Shire dam are below those of the other groups. The weights of all foals are
about 8 % of the weights of the dams.
I don't have time to post everything. So if anyone else is interested PM me your emails and I will send it to you if you're curious. I haven't read the whole thing, but hopefully will have time when the semester is over.