Page:Popular Science Monthly Volume 33.djvu/203

Rh muscular tissue or the nerves supplying it, but actually to the very reverse—namely, its paralyzing effects on the cardiac nerve mechanism. This may appear a strange idea to those unfamiliar with the advanced theories regarding the accelerating and restraining heart's nerve-forces. Nevertheless, it is quite consonant with the results of modern physiological investigations, which go far to prove that every function of organic life—no matter whether it be the expulsion of the urine, the peristaltic movements of the intestines, the throbbings of the heart, or involuntary respiration—acts under the immediate influence of a bifold nerve mechanism. For example, the human heart is endowed with two entirely different and opposing centers of nerve-force, and so retroactive are their respective functions that the sole duty of the one appears to be to regulate and control the functions of the other. To the former has been given the name of inhibitory or restraining mechanism; to the latter that of the exciting or accelerating nerve agency. Destroy or paralyze the inhibitory nerve-center, or arrest its power of communicating with the heart by dividing the vagus, and instantly its controlling effect on the cardio-motor mechanism is lost, and the accelerating agent, being no longer under its normal restraint, runs riot. The heart's action is increased, the pulse is quickened, an excess of blood is forced into the vessels, and from their becoming engorged and dilated the face gets flushed and the retina congested—all the usual concomitants of a general engorgement of the circulation being the result. Instead of paralyzing the vagus by section, and thereby arresting its inhibitory cardiac nerve-power; paralyze it through the instrumentality of a toxic agent, and precisely the same chain of phenomena will of necessity be the result. The most powerful paralyzer of the vagus we at present know of is atropia; and what happens when it is given in a full dose? Nothing more or less than the effects we have here attributed to the section of the vagus—tumultuous heart's action, quickened pulse, congested face and eyes, etc. Alcohol acts on the heart, I believe, in precisely the same manner as atropia does, although less strongly; that is to say, it quickens the heart's action, as well as apparently increases its power, by paralyzing its restraining or inhibitory nerve mechanism. This, however, is only the primary action of alcohol on the cardiac organ, for no sooner is the quantity administered sufficiently increased than all its at first apparently stimulating effects vanish. From its now possessing adequate power to paralyze the accelerating as well as the retarding cardiac nerve mechanism, the heart's action, therefore, now becomes diminished pari passu with the amount of the paralyzing agent employed, until at length (if a sufficiency be given) the cardiac