rticular period, lasting from twenty-four to forty-eight
hours, the commencement of which gives females, while its termination
gives males. In order that we may obtain a certain result, we must not
cause the same cow to be covered twice in succession at an interval too
short, for the (generative) substance of the bull preserves itself for
a time sufficiently long in the organs of the cow. In the experiments
made in Switzerland we have taken the cow at the first certain signs of
heating, for the purpose of obtaining heifers, and at the termination
of the heating for the purpose of obtaining males. The result of these
experiments is, that we do not yet know what is the relative length of
time which gives females, and the time which gives males; this would
form an interesting subject of examination. I am of opinion that
various circumstances must be regarded as influencing the relative
period, so as to alter the moment of (conception), and that the season
must exercise considerable influence. I am of opinion that in such
questions as that which forms the subject of my little work, we
physiologists should learn much from men of practice and experience,
such as you, who have afforded proofs of their knowledge. The best
results will follow when the raisers and experimentalists direct their
attention to the same object." I would here acknowledge the courtesy
and kindness of Professor Thury in so readily responding to my
inquiries. The experiments conducted in Switzerland were decisive in
support of Professor Thury's theory. In a trial of twenty-eight cows,
it proved correct in the whole number.

In the selection of the male, you will have to consider the faulty or
defective points in your cows with a view to correct them. As far as
possible--pedigree being right--you ought to purchase the bull that is
strong upon the points where your females are faulty. If this is not
duly attended to, the defect or malformation may be aggravated. But
although the bull selected possesses the excellence wanting in the
cows, he ought, of course, not to be very deficient in other points,
else the cure may be worse than the disease. If possible, he should be
taken from a pasture not superior to your own. Docility of temper in
male and female is indispensable. Inexpressible mischief may be done by
the introduction of wild blood into the herd, for it is sure to be
inherited. I have suffered seriously by this error.

To be good behind the shoulder,