A question may here be raised whether these humorous sayings, which are similar in all ages, have been handed down or re-invented over and over again. It must be admitted that the minds of men have a tendency to move in the same direction, and may have struck upon the same points in ages widely separated. In reading general literature, we constantly find the same thought suggesting itself to different writers, and I have known two people, who had no acquaintance with each other, make precisely the same joke--original in both cases. On the other hand, the rarity of genuine humour has given a permanent character to many clever sayings, and there has always been a demand for them to enliven the convivial and social intercourse of mankind. Their subtlety--the small points on which they turn--makes it difficult to remember them, but there will be always some men, who will treasure them for the delectation of their friends. It is remarkable that people are never tired of repeating humorous sayings, though they are soon wearied of hearing a repetition of them by others. A man who cannot endure to hear a joke three times, will keep telling the same one over and over all his life, and but for this, fewer good stories would survive. The pleasure derived from humour, while it lasts, is greater than that from sentiment or wisdom; hence we repeat it more in daily converse than poetry or proverbs, and the constant reproduction of it until it is reduced to a mere phantom, causes its influence to appear more transient than it is. And hence, although humour is generally "fleeting as the flowers," some of the jests, which pass with us as new, are more than two thousand years old. Porson said that he could trace back all the "Joe Millers" to a Greek origin. The domestic cat--the cause of many of our household calamities--was in full activity in the days of Aristophanes. Then, as now, mourners had recourse to the friendly onion; and if Pythagoreans had never dreamed of a donkey becoming a man, they had often known a man to become a donkey. If they were not able to skin a flint, they knew well what was meant by "skinning a flayed dog," and "shearing an ass." These and similar sayings, being of a simple character, may have been due to the same thought occurring to different minds, and this may be the case even where there is more point; thus, "an ass laden with gold will get into the strongest fortress," has been attributed to Frederick the Great and to Napoleon, and may have been due to both. The saying "Treat a friend as though he would one day become an enemy," has been attributed to Lord Chesterfield, to Publius Syrus, and even to Bias, one of the Seven Wise Men of Greece. Many may exclaim, "Perish those who have said our good things before us!"