(164.) _Causes of Rot._ If any one had been asked, thirty years ago, the cause or rather causes of the appearances which pass under the name of rot, he could not have enumerated them even in a day, for at that time each symptom was a disease, and as such was reckoned worthy of a separate and proximate cause. Nor could any person have had the courage to promulgate a common-sense opinion on the subject; for simple views regarding the diseases of domestic animals were then either not deemed worthy of a moment's notice, or, if considered, were swept at once, by the strong current of prejudice, into the foul ocean of predetermined disapproval. Opinions in cattle medicine were at that time valued according to the prolixity of their detail; and the more improbable the dependence of the effects upon the cause assigned, so much more was its discoverer lauded, and in like proportion was the chimerical fabric he had raised admired. Times are, however, now happily changed; that potent oculist, the march of intellect, has cleared the film from the public eye, and no one need, at present, be afraid to state the unaspiring fact, that _tubercles_ are the sole and proximate cause of the disease called rot. The observations of the late Dr Coventry, already quoted, would lead us to suppose that tubercles are of rare occurrence in the lungs of sheep, but in refutation of this assertion, I need only request the reader to take a ramble through a butcher-market, and he will perceive, even on cursory inspection, the fallacy of this conclusion. What the state of the liver is which is attended with flukes and hydatids, he has left us to make out. Chronic hepatitis, which accompanies tubercles in the liver, goes for nothing as a disease of sheep, and therefore does not require a notice; besides, it is not rot, and is quite incompetent of itself to cause it. As for the scurvy of which he speaks, he evidently means the disease now generally known by the name of _Pining_, but which, as it has no connexion with rot, and has only become prevalent within the last sixteen years, could not be very well known to him. The following questions will naturally occur to many of my readers. What gives rise to these tubercles? what are the predisposing causes which lead to their formation? and, when formed, how do these apparently unirritating bodies produce effects so baneful? Queries like these, however, cannot shortly be replied to, leading, as they do, to discussions which embrace many curious theories; but as the negative mode of teaching is often of avail where the positive or more direct would fail to bring conviction, I shall, before proceeding to allude to what the causes are, endeavour to state what they are not.