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.
[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.
A few words are first of all necessary to indicate precisely what anæsthesia is.
By definition, an anæsthetic is a substance which, without paralysing the activity of the heart and the respiration, abolishes sensibility. Indeed, whenever general sensibility is abolished, there is, at the same time, abolition of consciousness, of intelligence, and of memory. Another characteristic of an anæsthetic is that its action is of a transient nature. At the end of a certain time, it disappears; and then intelligence, consciousness, and memory return gradually with sensibility.
It is well known that the admirable discovery of general anæsthesia, allowing operations to be performed on man without the accompaniment of pain, was due to chance. It was an American dentist, Horace Wells, and his colleague, Morton (and others also perhaps), who discovered by chance that protoxide of nitrogen (commonly called laughing gas) has the power, when inhaled, of annulling all sensibility to pain for a certain length of time--sufficiently long for a surgical operation (1840). Then they discovered the effects of ether (1842). Since then, many other anæsthetics have been introduced, notably chloroform, prepared by Soubeiran in 1832, but the anæsthetic properties of which were only discovered in 1847 by Flourens and Simpson; so that physiologists and surgeons are now quite familiar with the mode of action of anæsthetics.