A popular delusion is often the basis of a great abuse. If at one time witches were burnt by countless thousands, it was at a period when implicit faith in the reality of diabolic conspiracy was undisturbed by sceptical questionings. Human slavery existed for centuries, not only because it was profitable, but because it came to be regarded as the only conceivable permanent relation between the negro and the white man. The Spanish Inquisition existed for ages, because the pious Spaniard could not believe that the good men who upheld, encouraged, and promoted its activity could be liable to error, or actuated by other than the loftiest principles. Men find themselves deluded not merely because of their faith in the integrity of their fellow-men, but because they have also extended that faith to the accuracy of their opinions. There can be no doubt of the fact that public apathy regarding the abuses of vivisection as now carried on without limitations or restrictions is grounded upon the great anaesthetic delusion. This misinterpretation of facts, this misunderstanding of scientific statements, constitutes the most singular delusion of the present time. What is anaesthesia? It has been defined as a state of insensibility to external impressions, sometimes introduced by disease, but more generally in modern surgery by the inhalation of the vapours of ether or chloroform. The discovery of the properties of these drugs constitutes a very interesting chapter in the story of scientific achievement; but in this connection the chief point of interest lies in the fact that the most wonderful of all advances in medicine was made without resort to the vivisection of animals. Sir Benjamin Ward Richardson, an English scientist who had much to do with its various methods, tells us that "the instauration of general anaesthesia came from experiments on man alone; there is no suspicion of any experiment on a lower animal in connection with it"; and Professor Bigelow, of Harvard Medical School, as we have seen, makes the same statement. The extent to which insensibility may be carried depends entirely on the amount of the vapour inhaled. Suppose the quantity to be very small. Then the result will be a diminished sensibility, without entire loss of consciousness. Let the quantity inhaled be considerably increase, and we may produce a profound stupor with muscular relaxation, the eyes are fixed, and the eyelids do not respond when the eyeball is touched. There is now deep anaesthesia, and complete unconsciousness to the surgeon's knife. The borderline between life and death is not distant; and if still more of the anaesthetic is administered, we may reach a condition from which there is no awakening. The skill of the anaesthetist is not unlike that of a pilot, who needs to know just how far the ship may be steered in a difficult channel without running upon the rocks.