FERTILITY 655 



bouillon culture to a cow, the placenta was found covered with typical 

 exudate rich in bacilli. It is probable, therefore, that entrance 

 through the alimentary canal is the most frequent way by which the 

 disease is spread. There is some experimental evidence that cows 

 may acquire immunity to the disease, at least temporarily. Investiga- 

 tions show also that mares, sheep, goats, dogs, and guinea-pigs may 

 be infected with the bacillus experimentally, but in all probability 

 the disease is ordinarily confined to cattle. The abortion microbe 

 is, stated to be, oval or rod-shaped, between one and two microns in 

 length, and non-motile. It sometimes occurs, singly, but , in many 

 places the bacilli are collected in dense groups, or colonies. The 

 microbe associated with abortion outbreaks in sheep is said to be a 

 vibrio and therefore totally different.^ It has been isolated and used 

 experimentally to infect pregnant ewes. Pregnant cows, however, 

 cannot be infected' by it. Horses and swine may also suffer from 

 abortion of an epizootic nature. 



The external use of antiseptics is said to prevent the spread of 

 contagious abortion by means of disinfection, but isolation is the most 

 effective method.^ Vaccine treatment is an efficacious preventive. 



The causes of abortion in sheep are dealt with at some length' by 

 Heape in the paper already referred to.^ Statistical evidence shows 

 that an excessive proportion of shearling ewes in a flock is associated 

 with a relatively high percentage of abortion, and that ewes of 

 particular breeds in certain districts, or run on certain subsoils, are 

 more liable to abortion than the average for the breed in question. 

 Thus Lincoln sheep run on the Wolds suffer much more from abortion 

 than sheep of the same breed in other districts. The Southdown and 

 Hampshire Down 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 tlie principal factors 

 which influence the percentage of abortion. Unsuitable food, causing 

 indigestion or other ailments, and poor food, resulting 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 



^ Heatley, "Abortion in Sheep," Board of Agric. Dept. Gommittee Report. 

 Printed by the Suffolk Sheep Society, Bury St. Edmunds, 1914. 



2 Board of Agriculture Leaflet, No. 108, 1904. 



3 Heape, "Abortion, Barrenness, and Fertility in Sheep," Jour. Royal Agric. 

 Soc, vol. X., 1899. See also Fleming, loc. cit. 



