NUTRITION AND FERTILITY 373 



Scarcity of ripe follicles at tupping time must clearly result 

 either from retardation in follicular development or from an 

 unusual amount of follicular degeneration, either recently or at 

 some previous period in the animal's lifetime. Degeneration of 

 follicles is by no means uncommon in the ovaries of sheep, and 

 appears to be most frequent in those which have attained to 

 from one-eighth to one-half the dimensions of the mature follicle. 

 It may set in, however, at practically any stage of development. 

 The follicle, instead of continuing to grow, undergoes a series of 

 retrogressive changes, which result in the shrivelling up of the 

 ovum and the ultimate absorption of the entire contents of the 

 follicle. There can scarcely be any doubt that the degeneration 

 is usually the result of an insufficiency of stimulating ipower at 

 the disposal of the ewe. 



That scarcity of mature follicles in sheep's ovaries at tupping 

 time may be due to retardation of growth is a conclusion that is 

 based on inference rather than on direct observation, for little 

 is known concerning the rate of development of the Graafian 

 follicle. There is every reason for believing, however, that the 

 process of ripening can be very largely influenced both by 

 insufficiency of food supply on the one hand, and by artificial 

 stimulation on the other. 



This fact has been perfectly well realised for years past by 

 certain individual flockmasters, who have consistently practised 

 the methods of flushing or artificially stimulating their sheep by 

 means of an extra supply of special food at the approach of the 

 breeding season. It is somewhat surprising, however, that no 

 precise records of the effects of flushing upon fertility had been 

 collected until quite recently, when the Highland and Agricultural 

 Society of Scotland undertook an inquiry upon this subject. 

 The absence of published information may perhaps explain the 

 prevalent ignorance of the results of flushing among many sheep- 

 breeders who have never adopted it. 



In a preliminary report upon the Highland Society's investi- 

 gation 1 containing the lambing statistics for various Scottish 

 breeds in the year 1905, it is shown that the percentage of lambs 

 born was, as a rule, largest among flocks which had been 

 subjected to a process of artificial stimulation. The method 

 adopted was to feed the ewes upon turnips, oats, dried grains, 

 maize, or other artificial food at the tupping time and for about 

 1 Marshall, Proc. Royal Soc. B, vol. lxxvii. 1905. 



