618 THE PHYSIOLOGY OF REPRODUCTION 



statistics show that a heavy rainfall during gestation is associated 

 with a high degree of abortion. Over-exertion (as from jumping 

 ditches), fright (from strange dogs or shooting), are usually 

 credited with producing abortion in sheep, but Heape remarks 

 that such causes are not truly responsible unless the ewes are in 

 a susceptible condition. The main conclusion reached is that 

 the food and the resulting condition of the ewes are the principal 

 factors which influence the percentage of abortion. Unsuitable 

 food, causing indigestion or other ailments, and poor food, re- 

 sulting in bad nutrition, are held to be mainly responsible. 

 Heape states, however, that it is not the kind of food so much as 

 the condition of the food which is most liable to be at fault, 

 while the schedules show clearly that a poor condition of ewes 

 during gestation is associated with a relatively high percentage 

 of abortion. " Sheep-stained " pasture {i.e. pasture grown 

 with the aid of sheep manure or on which sheep have been run 

 for a considerable time previously) is credited with causing 

 abortion, and there is strong evidence in support of this view 

 in cases where rank or over-stimulated growth results.^ 



As already noted, the Dorset Horn and Lincoln breeds of 

 sheep suffer most from abortion.^ In the case of the former 

 this may result partly from inbreeding, since Dorset Horn ewes 

 served by Hampshire Down rams are less liable to " slip lamb " 

 than those served by rams of their own breed. It is possible, 

 therefore, that the abortion may be due to a want of vitahty 

 on the part of the developing embryo, the cross-bred young 

 possessing a superior vigour. Abortion among Lincoln sheep 

 has been known to reach thirty, forty, or even fifty per cent., 

 and so to assume an epidemic form. Wortley Axe,^ who reported 

 on an outbreak of abortion among the Lincolnshire flocks in the 

 season of 1882-83, was disposed to attribute it to debility, 

 arising largely from foot-rot and exposure to cold winds and 



1 Abortion in sheep may result from more exceptional causes. Thus 

 it is recorded that a. large proportion of a certain flock of Cheviot ewes 

 slipped lamb after a gale which blew down a number of Scotch fir-trees, 

 the abortion resulting, in the owner's opinion, from the animals eating the 

 branches and bark. See Marshall, loc. cit. ^ Heape, loc. cit. 



" Wortley Axe, " Outbreak of Abortion and Premature Birth in the Ewe 

 Flocks of Lincolnshire during the Winter and Spring of 1882-83," Jour. 

 Boyal Agric. Soc, vol. xxi., 1885. 



