I have skipped lightly, I admit, over a considerable interval between primitive man and Benozzo Gozzoli. But consider further that during all that time the uses of the right and left hand were becoming by gradual degrees each day still further differentiated and specialised. Innumerable trades, occupations, and habits imply ever-widening differences in the way we use them. It is not the right hand alone that has undergone an education in this respect: the left, too, though subordinate, has still its own special functions to perform. If the savage chips his flints with a blow of the right, he holds the core, or main mass of stone from which he strikes it, firmly with his left. If one hand is specially devoted to the knife, the other grasps the fork to make up for it. In almost every act we do with both hands, each has a separate office to which it is best fitted. Take, for example, so simple a matter as buttoning one's coat, where a curious distinction between the habits of the sexes enables us to test the principle with ease and certainty. Men's clothes are always made with the buttons on the right side and the button-holes on the left. Women's, on the contrary, are always made with the buttons on the left side, and the button-holes on the right. (The occult reason for this curious distinction, which has long engaged the attention of philosophers, has never yet been discovered, but it is probably to be accounted for by the perversity of women.) Well, if a man tries to put on a woman's waterproof, or a woman to put on a man's ulster, each will find that neither hand is readily able to perform the part of the other. A man, in buttoning, grasps the button in his right hand, pushes it through with his right thumb, holds the button-hole open with his left, and pulls all straight with his right forefinger. Reverse the sides, and both hands at once seem equally helpless.