2. _In every case the evidence of the teeth is secondary to direct and substantiated testimony_; for as there is no limit to possibility, so no man can be prepared to say what Nature may or may not do. In the absence, however, of positive and corroborated testimony, the teeth become the best evidence, and that on which reliance should be placed. When opposed to the indications of the mouth, the oath of a single individual, for obvious reasons, would be of no weight. A foal can hardly be born without many parties being cognizant of the fact--the colt cannot change its master without several persons being made aware of the transaction--and horses, for honest purposes, are not generally sold or bought in secret. Proof of the age can generally be adduced, if the parties interested think proper to seek it; or when it is not possible to adduce such proof, the teeth deserve more confidence than an uncorroborated assertion. An individual may be interested to mis-state, or may be mistaken in his belief; whereas the teeth, being natural growths, are removed from such suspicions. 3. _Some of the causes which induce certain persons to doubt_ the possibility of the horse's age being accurately told from the teeth, are not difficult to explain away. The Jockey Club has seen reason to declare, that all thorough-bred animals shall be born on the 1st of January, or if any should make their appearances at a later period, such shall be esteemed one year old when the 31st of December has expired. All blood horses have but one birth-day, nor do they in that respect differ from their brethren of the coarser breeds; only those of the last description are supposed to begin their existences upon the 1st of May. If a racer has seen six Januaries, it is said to be six years old; and if a nag had looked upon half a dozen Mays it would be pronounced to be of a similar age. These customs are convenient, as affording a point from which to date the age of an animal; but under such regulations, confusion will and does frequently arise. In a long number of years, a few months may be of little importance; but at the earlier period the difference of several weeks may, in the calculation of the age, be a serious matter. I will endeavour to show how far, in an extreme case, confusion may be created by the operation of these customs, and to prove, that he who should read the teeth correctly, would be unable to satisfactorily pronounce the accepted age of a colt. According to the received laws, a blood foal dropt on the 31st of December, and a foal not thorough-bred, born on the 30th of April, would each, the second day of life, complete the first year of its existence. Let it be supposed that a blood mare bore a foal in the latter end of December--the animal would be entered in the stud book according to the year of its birth, but for obvious reasons could never be put into training; it would be kept until another January arrived, when, although but one year and a