APK | 902 



A CRITICAL PERIOD IN THE DEVELOPMENT 

 OF THE HORSE. 



INTRODUCTORY". 



At a meeting 1 of the Central Veterinary Medical Society of 

 London, at which I exhibited a number of young horse embryos, 

 I had barely time to allude to what may prove a subject of some 

 practical importance, viz., the apparatus provided for nourish- 

 ing the embryos during the early weeks of development. This 

 apparatus (which consists mainly of what are known as the foetal 

 appendages) I was led to consider from a breeder's point of view 

 by Lord Arthur Cecil asking me, about a year ago, if I could 

 account for so many mares breaking service from the sixth to the 

 ninth week. At the time I could only answer that I agreed 

 with his lordship in believing it was in many cases due to the 

 detachment and escape of an embryo. I have frequently found 

 mares all right, as far as I could judge, at the end of the sixth 

 week, and all wrong some weeks later. This seems to be not an 

 uncommon experience, more especially at the beginning of the 

 breeding season, hence it is always urged by experts that mares 

 should be " tried " frequently during at least the first two months. 

 If holding at the end of the ninth week no further trouble is, as 

 a rule, anticipated. But no one has, as far as I am aware, 

 explained why the breeder experiences so many difficulties during 

 the earlier weeks. According to the evidence obtained by the 

 Royal Commission on Horse Breeding, it appears that about 40 

 per cent, of the mares selected for breeding fail to produce 

 offspring during any given year. This is a very high percentage 



1 -1th March (see the Field, 13th March 1897). 



