(1) Prior to pregnancy the calcium content in
the blood of full-grown rabbits was found to vary "between
13 and 15 m.gm. per 100 c.c. serum, with
suggestions of a significantly regular rise and fall.
During the early period of pregnancy no difference
between the serum-calciurn content of the pregnant and
the non-pregnant does was found.
(2) 7 to 10 days before parturition the serum-calcium,
then high, commences to fall and one, two
or three days before parturition there is a further
and more sudden fall to a minimum.
(3) After parturition the calcium content is
restored to normal by a rise as sudden as was the
previous fall, but about the 19th day of the lactation
period, or thereabout, there is a second sudden
fall to often a still lower minimum than was noted
before parturition. Following this fall there is a
sudden return to normal, but in some cases the return
ends in a remarkable maximum of calcium in the serum,
higher than any previously exhibited. Soon afterwards
there is a return to normal, the calcium level
then remaining steady till the end of the lactation
(4) Data collected from several rabbits of both
sexes, excluding those relating to the periods of
pregnancy and lactation, show little indication of
any sex-dimorphism in calcium-metabolism. If, however,
these data are computed and the true mean with
probable error found for each sex it is seen that indeed
there is a significant sex difference. 'The
difference between the sexes was found to be more
than five times its probable error, and if five
times is taken as the limit of significance there is
sex-dimorphism, the males having a higher serum-calcium
content than the females.
(5) During the period of gestation foetal
blood contains less serum-calcium than maternal until
the last week of pregnancy when the foetal serum-calcium
equals the maternal and in some cases surpasses
it. This is to be explained by the sudden
decrease in serum-calcium in the maternal blood.
After parturition when the maternal value is again
constant the maternal serum-calcium level is higher
than the foetal. This relation persists till the
young rabbit is about a month old when its serum-calcium
level approaches that of its mother.