Further, for pain to exist the impression must be durable and not fugitive. The assertion of the _ego_ is not enough. It must be prolonged. A pain, however intense we may suppose it to be, which traverses the organism for a second and which leaves no painful echo behind it, is no real pain. I will allow any one to inflict the most excruciating tortures on me if he can assure me that, at the end of one second, I shall have lost all recollection of the suffering and that no trace of the torture will remain. The extraction of a tooth lasts perhaps only half a second, but you remember it all your life. In any case, for several minutes the pain continues to be atrocious. Therefore we may certainly consider that pain is a phenomenon of memory. Pain is an empty word for every being that has no memory. From these facts we may evolve the general conclusion that, under penalty of falling into vulgar anthromorphism, we cannot apply to the pain of animals the data which have been gathered on human pain.[5] With man, the developed intelligence and vivacious memory enable pain to acquire an extreme intensity. But with animals, in proportion as the intelligence lessens and the memory becomes more rudimentary, so does pain diminish, and, without having the right to be very affirmative, as we are in profound darkness concerning the consciousness of animals, it appears to me that, as we descend the scale of the animal kingdom, pain rapidly becomes very hazy, scarcely perceived, and as indistinct as the consciousness of the _ego_. We have, therefore, the right to perform vivisection on beings which, because they possess no _selfhood_, do not suffer. Now, this absence of memory, consciousness, and intelligence extends assuredly over the whole of the vegetable kingdom, almost certainly over all the groups of the invertebrata, and also probably over all the inferior vertebrata. Finally, there remain only the mammalia and birds which are capable of real pain. Although this pain may be obscure and indistinct, it is certain; and we must take it into consideration or fall into barbarism; therefore we shall restrict the problem of vivisection to the vivisection of superior animals, who, alone, are capable of suffering. FOOTNOTES: [4] The true vegetarian is an extremely rare person. The usual so-called vegetarian ought more properly to be called a non-meat eater, for he does not scruple to consume milk (intended by nature for the calf) and milk products (cream, cheese, and butter) and eggs, nor to wear garments made of wool and leather.--(W. D. H.) [5] In the little leaflet already referred to, quotation is made of a sentence from Professor Pritchard, which says that the various animals have a skin of different thickness, but that sensibility is the same among all, including man. It seems to me that Professor Pritchard has scarcely looked into the questions of general psychology. CHAPTER III CONCERNING ANÆSTHESIA IN VIVISECTION