CHAP. v. PERIOD OF GESTATION IN COWS. 119 



bull a measure which cannot be too much deprecated, for the most 

 efficacious mode of obtaining this object undoubtedly consists in keep- 

 ing them in good heart. The time when a cow is in season, is known 

 by her restlessness, or her riding on other cattle ; and by an inflamed 

 appearance of the external parts, accompanied by a discharge from the 

 vagina. These symptoms, generally, do not continue more than about 

 24 hours, and do not return till the expiration of 20 or 21 days. When 

 conception has taken place they disappear. 



The period of gestation, or the time during which the cow goes with 

 calf, varies much. A bull calf usually goes about forty-one weeks, with 

 a difference of a few days either wa} r ; a cow calf coming in less time. 

 From 282 to 285 days may, therefore, be assigned as the average period 

 of gestation. At the close of this period the cow usually produces one calf; 

 though instances sometimes occur when two, or even three, are brought 

 forth. It may not, however, be useless to remark, that some cows are 

 naturally barren, and this is said to be the case when a male and female 

 calf are produced at the same time. The male animal is perfect in all 

 respects; but the female, which is denominated a free marten, is, 

 generally speaking, incapable of propagating her species. There are, 

 however, a few instances on record of her breeding. She does not 

 differ very materially, in point of form or size, from other cattle, 

 though the flesh is erroneously supposed to .be greatly superior in 

 flavour and fineness of the grain. 



The late Earl Spencer has left us data as to the period of gestation 

 in the cow, founded on observations on 110 less than 764 of these 

 animals. 1 He says : 



" The shortest period of gestation when a live calf was produced was 

 220 days. Any calf produced at an earlier period than 260 days must 

 be considered as premature, and any period of gestation exceeding 300 

 days must also be considered as irregular." 



He states that, out of the 764 cows he observed, 314 calved before the 

 284th day and 310 after the 285th day, thus showing that the average 

 period of gestation is about 285 days, as above stated on the authority of 

 Mr. Torr, who was an eminent breeder of Shorthorns in Lincolnshire. 

 It is a generally received opinion that when the ^eriod of gestation 

 exceeds forty-one weeks a bull calf may be expected, and observation 

 and experience have demonstrated that there is some foundation for 

 this belief. 



As cows are very subject to abortion (see page 557) when improperly 

 treated during gestation, they ought to be watched with more than 

 ordinary care through the whole of that period, and particularly the 

 latter portion of it. The principal causes of abortion are violence or 

 accidents, too good or too poor condition, hereditary predisposition, 

 some epidemic or other influence ; and last, though not least, con- 

 tagion, or a tendency to slip the calf, being propagated from one cow 

 to another. Ergoted grasses, which are often to be found in ditches 

 and swampy places, in wet seasons, are probably one of the causes of 



1 -'Journal of the Royal Agricultural Society," vol. i. 1st series, p. 165. 



