FERTILITY 613 



this cause being respectively 4-11 per cent, and 4 per cent. The 

 Southdown breed were found to occupy an intermediate position 

 (the percentage of abortion being 2'86 per cent.), while the other 

 breeds investigated showed a smaller percentage of abortion. 

 Among Scottish breeds the percentage of aborting ewes does 

 not generally exceed 2 per cent., as far as could be ascertained ; 

 but with Blackfaced ewes it may be as much as five, or even 

 a considerably higher number, as a consequence of any special 

 adverse circumstance.^ It is possible, however, that the per- 

 centages of abortion are actually somewhat higher than they 

 appear, since its occurrence during the early stages of pregnancy 

 is not readily detected, and consequently some of the ewes 

 which were entered in the statistical returns as barren may 

 in reality have aborted. 



Among cattle in Great Britain the frequency of abortion, 

 according to Heape,^ is not less than ten per cent, of the total 

 number of animals selected for breeding, and there can be 

 no doubt that in certain districts it is often very much higher, 

 especially where contagious or epidemic abortion occurs. Heape 

 states further that from ten to twelve per cent, of abortion is 

 not unusual in herds in which no contagious abortion is proved 

 to exist. 



There are no data available on which to compute the fre- 

 quency of occurrence of abortion among horses, but the ex- 

 perience of breeders shows that the losses arising from this 

 cause are very considerable, and that they are greatest amongst 

 the better-bred animals. One of the earlier reports of the 

 Koyal Commission on Horse-Breeding stated that in this country 

 in any given year no less than forty per cent, of the mares 

 chosen for breeding fail to produce foals, but to what extent 

 this result is due to sterility or how far it may be ascribed to 

 abortion does not appear to have been ascertained. 



The causes of abortion are diverse, and may be mechanical, 

 psychological, physiological, or pathological. Dehberate abor- 

 tion among civihsed European nations is a criminal offence 

 punishable by law, but nevertheless is not infrequently carried 



' Marshall, "Fertility in Scottish Sheep," Trans. Highland and Agric. 

 Soc, vol. XX., 1908. 



' Heape, The Breeding Industry, Cambridge, 1906. 



