If fat, they will be averse to becoming pregnant, and considerable annoyance will, in all likelihood, be experienced. A moderately low diet is most suitable for ewes, for some time before the ram is admitted, in the same way that fruit trees, when unproductive in a rich soil, are rendered fertile by placing straw and stones between their roots and the too nutritious earth. A rather poor diet, also, during pregnancy, will be found to obviate many of those risks which are sure to be incurred from repletion during this period. [15] Dr Cline, in a communication to the Board of Agriculture, observes on this point: "Experience has proved, that crossing has only succeeded in an eminent degree, in those instances in which the females were larger, than in the usual proportion of females to males, and that it has generally failed when the males were proportionally large." [16] It was owing to a peculiar view taken of this maxim, that so enormous sums were asked and given, for the hire of rams, at the time Mr Bakewell brought the new Leicester to perfection. That gentleman would never have obtained 1200 guineas for the hire of three rams if the speculators had not intended to procure nearly similar prices for the use of the offspring of these animals; and it may be pretty safely affirmed, that this traffic was ultimately the cause of much mischief to the breed in question, by inducing many to speculate on what was likely to prove a fashionable article, without caring much for the endurance of the really valuable points. [17] Dr Sturm, professor of Agriculture, at Bonn, says, that a new race may be produced in the same number of years as are required for perfecting the teeth. [18] Sheep are as liable to distortions of the skeleton as other animals. The Museum of Guy's Hospital contains a very good specimen of distorted spine taken from a sheep.