notable instance, and in one or two less notable, nitrous-oxide gas, the gas now so commonly used by dentists as an anæsthetic, has been resorted to as an habitual stimulant and narcotic; but the rarity of its use prevents the necessity of doing more than referring to it in this place, and once perhaps again in the sequel. Of the other agents it may be said, in limine, respecting the extent of their use, that the alcohols and tobacco stand first on the list in our civilized life. Next after these come opium, absinthe, chloral hydrate, chlorodyne, ether, and chloroform. The other substances are local in the range of their employment. Hasheesh is an Eastern luxury; amanitine a Kamtchatkan luxury; arsenic a Styrian luxury; red-thorn apple a luxury of the Indians of the Andes, under the sweet influence of which they enter into communion, as they believe, with the spirits of their departed dead—the best excuse I have ever heard given for the use of any of these indulgences whatsoever.
As we cast our minds back upon this long list of toxical instruments for the delight of man, we are struck with the widely apparent difference that seems to exist between them. The difference, however, is not so great as it may seem, for between the physiological action of one and the other there is an analogy of action in certain particulars which is singularly striking. As a rule, the key-note of the action of these agents, if I may use such a simile, is through one particular element where many elements enter into their composition. Where nitrogen is present as an element, a definite line of action of the agent is marked out; when a hydrocarbon radical is dominant—that is to say, when such a radical forms the chief part of the compound—the influence of that is most definite; while the influence of one disturbing principle on another may be most clearly traced in other cases as a neutralizing influence, one influence reacting upon the other.
We have at hand many instances of this kind for illustration. Alcohol and tobacco are the most ready examples. In the alcohols, whichever one of the family of alcohols we may take, from the least dangerous wood-spirit, through the more dangerous grain-spirit, up to the much more dangerous potato-spirit, there is one agency at work, a hydrocarbon radical, methyl, ethyl, amyl, according to the alcohol used, which, with different degrees of intensity, plays the same part, producing similar series of phenomena. In tobacco we have a less decisively known combination at work, but we have in that combination the element nitrogen, the introduction of which causes a new development of nervous phenomena, the analogous action of which can be traced through some other complex organic compounds containing the same element—nitrogen. In chloroform, again, we have a hydrocarbon radical playing nearly the same part as the radical methyl of methylic alcohol, but with chlorine interposing to modify the simple narcotic action of the radical, and greatly to increase the danger of
