326 INFLUENCE OF THE BULL ON UTERO-GESTATION. 
male animal by whom the cow was impregnated did not appear 
to have any influence up to the time at which this average was 
taken ; but in the autumn of 1840, I bought a bull, which I had 
sold as a calf in the spring of 1836, and the calves by him were 
first dropped in the beginning of last August: since then I have 
had sixteen calves by him, and, to my surprise, have found that 
the average period of gestation of the dams of these sixteen 
calves was two hundred and ninety and a quarter days. Upon 
this I applied to the gentleman who had bought the bull from 
me, and from whom I had bought him back, to let me have the 
period of gestation of each of the cows who bred calves by this 
bull while he had him in his possession, and he sent me an 
account of the respective periods of the gestation of fifty-nine 
cows in calf by this bull, and I find that the average period 
was two hundred and eighty-eight days ; and if you add to the 
periods of gestation of these fifty-nine, the periods of gestation 
of the sixteen which have occurred since he has been in my pos- 
session, the average of the whole seventy-five is two hundred and 
eighty-eight days and a half. 
“ It appears therefore quite clear,” continues his lordship, 
*' that cows in calf to this bull, on the average, are about four 
days longer before they calve than those in calf to other bulls. 
It appears also that of the 764 cows on which I formed my 
average in my own herd from a great many different bulls, 185 
went less than 281 days, while not one of the 75 cows in calf to 
this bull have done so. On the other hand, of the 764 cows 
111 went above 289 days, or rather more than one-seventh of the 
number ; while by this bull 29 out of the 75 went above 289 
days, or between one-third and one-half.” 
Since the above was written his lordship has given me the 
average period of gestation in 931 cows in calf to other bulls, 
and of 79 cows in calf to the bull in which this peculiarity was 
first observed; from which it appears perfectly clear that the du- 
ration of pregnancy in cows put to this animal is, on an average, 
four or five days longer than in other bulls. This being the case, 
it is impossible to account for the fact in any other way than by 
answering the question proposed at the commencement of this 
investigation affirmatively, and by concluding that the male can 
influence the duration of the foetus in utero. 
