654 THE PHYSIOLOGY OF REPRODUCTION 



eighth week ; for unless the villi appear in time, and succeed in 

 coming into sufficiently intimate relation with the uterine vessels, 

 the developmental process is of necessity for ever arrested." 



Ewart discusses briefly the external conditions and circumstances 

 which are likely to lead to abortion, and provides some useful 

 practical hints as to the best way to treat mares in order to prevent 

 them from " slipping foal." He remarks that the horse is a peculiarly 

 high-strung, nervous animal, and is easily affected by sudden changes 

 in its surroundings, especially during the breeding season. Such 

 changes are, no doubt, often responsible for setting up disturbances 

 in the nervous system, and so inducing abortion, more particularly 

 at that period of development at which the h'xation of the embryo 

 to the uterine wall is relatively insecure. 



Abortion in cows is said to be commonest during the first month 

 of pregnancy. According to Wallace 1 the usual causes are the 

 following : (1) Eating ergotised grass ; (2) injury due to horning by 

 other cattle, hunting by dogs, or shaking and bruising in travelling, 

 etc. ; (3) physical strain, resulting from walking over too soft land, etc. ; 

 (4) very cold or foul water, or frozen turnips, etc. ; (5) superpurgation, 

 whether occurring naturally or as a consequence of dosing by physic ; 

 (6) contagion from other cows affected by epidemic abortion. This is 

 said to be the commonest and at the same time the most dangerous 

 cause of abortion. 



Bang 2 has shown that contagious, epidemic, or epizootic abortion 

 in cattle is due to a specific bacillus which he has been able to isolate 

 and cultivate in oxygenated glycerine-bouillon or serum-gelatine 

 agar. The germ causes the formation of a brownish-yellow exudate 

 between the chorion and the mucous membrane of the uterus, and 

 more particularly around the cotyledons, but the affected area may 

 be considerably greater. 3 Bang has shown experimentally that the 

 germs may be carried to the seat of the disease by the blood after 

 intravascular injection, and furthermore, that they can be absorbed 

 through the alimentary canal. Thus, after administering some 



1 Wallace (R), loc. cit. Wallace states that after abortion in cattle the 

 placenta adheres to the cotyledons, and should be removed artificially ; other- 

 wise it is liable to undergo a process of rotting, sometimes resulting in septicaemia 

 and death. See Fleming, Veterinary Obstetrics (Craig's Edit.), London, 1912. 



2 Bang (B.), " Infectious Abortion in Cattle," Xat. Vet. 8oc., Liverpool, 

 25th July 1906. 



3 Report of the Departmental Committee appointed by the Board of Agriculture 

 and Fisheries to inquire into Epizootic Abortion, London, 1909. According 

 to this Report, nothing more than a quite subsidiary role in the spread 

 of the disease can now be referred to the bull. For further information 

 and references see Surface, "The Diagnosis of Infectious Abortion in 

 Cattle," Report of Kentucky Exp. 8tat., 1912 ; " Notes on Infectious Abortion 

 in Cattle," Science, vol. xxxvi., 1912; and "Bovine Infectious Abortion 

 Epizootic among Guinea-Pigs," Jour, of Infectious Diseases, vol. xi., 1912 ; also 

 McFadyean, " Epizootic Abortion of Cattle," Jour. Comp. 1'ath. Ther., 1921. 



