The nerve-current which transmits sensations to the brain, and the orders of the will to the extremities of the body, requires a certain time to travel in. Impressions coming from without are not perceived at the instant they are produced, they travel along the nerves at the rate of 20 to 30 métres (25 to 40 yards) in a second, which is the same speed as that of the carrier pigeon, of a hurricane, or of a locomotive engine at its quickest, but very much less than that of a cannon ball. For instance, we can only be conscious of an injury to one of our feet about one twentieth of a second after it has actually occurred, and the commands of the will proceed equally lowly from the centre to the peripheries of the nervous system. In he human body the time thus occupied is unimportant, but let us take the case of a whale, where the telegraphic network of the nervous system is far more extensive. A boat attacks the whale, and a harpoon is driven into its tail. The impression thus produced has totravel over some forty yards before reaching the head-quarters of the will; a second is thus lost. How long a time is then required for reflection? That must depend upon circumstances; but at any rate it is certain that the will has need of some definite amount of time for its decision. The order to capsize the boat is despatched to the tail, but another second must elapse before the telegram reaches its destination, and in the time thus employed the whaling boat has pulled off and escaped the danger.