SECT. VII. (Book 7)
CHAP. I. Of Opiates, or such Medicins as make a Man sleep.
AFter Medicins that are Cordials, Hypnoticks [or sleepy Medicins] succeed accor∣ding to the order of Method. For Sleep, when it comes upon one moderately and seasonably, is in it self the most cordial remedy. But this disposition [to sleep] is not used to overtake a man either always when, nor as it ought to do, but oftentimes disorders us either by its unwelcome presence, or by its too long absence. By the right * 1.1 rule of Nature, Sleep and Watching ought, like Castor and Pollux, to give place to each other, and change turns, according to the just limits of their reign. This vicissitude, as long as it is well observed, conduces very much not onely to the preservation of health, but to the improvement of the faculties of our minds. But if the dominion of either be too long continued, it thereupon immediately ceases to be possible, ut sit mens sana in corpore sano, i. e. for our mind and body to be both in health. Through immoderate sleep, all the faculties both our natural and animal functions grow very dull, in so much that thereby a man becomes more fit for his Grave than Humane society. On the contrary, long watching wasteth the strength of a man, and either weakeneth or per∣verteth the powers of Life. Wherefore among such Remedies as are suitable to our wants, the wise Creator hath abundantly provided for our necessities; to wit, that it should be in our own power to cause or repel sleep or watchfulness as often as we think it convenient; or if they be offensive at any time either in defect or excess, to moderate them. What Medicins (and by what manners of operation in humane bo∣dies, they) use to procure these wished effects, lies now upon me to shew you; and first of all, I shall speak of Opiates, or such Medicins as cause sleep.
That you may the better understand what Hypnotick or sleepy Medicins do, and with what kind of operation upon the brain, animal spirits, and other parts, they pro∣cure sleep, I should repeat in this place, what I have elsewhere at large discoursed con∣cerning * 1.2 the nature, subject, causes, and effects of sleep. For I have demonstrated the immediate subject of sleep are the animal spirits, not all of them, but onely such as in∣habit the Brain and the Nerves, which are an appendage to it: that is to say, those which perform the duties of all the senses, and every sort of spontaneous or voluntary motion; always excepting those that serve onely to execute the necessary orders of meer Nature and Life.
Having therefore premised these things, we must enquire concerning Opiates, first * 1.3 of all how they work upon the animal spirits, so that by the influence, as it were, of such a Medicin, they immediately sink and lie down, as if they were bound in Fetters, neglectful of their several offices. Secondly, We must shew in what part sleepy Me∣dicins begin their operation; that is to say, whether in the Stomach, or the Brain, or whether they do it together, or successively in both. Thirdly, We must determine how far Opiates extend their operations, whether to the spirits of the Brain onely, and those that are inhabitants of its appendages as being the onely ones that are ca∣pable of natural sleep; or whether they reach also to others belonging to the Cere∣bellum [or hinder part of the Brain] and those that rule in those Regions. Fourthly and lastly, It will be worth our while to add some notable effects and accidents, to∣gether with the natural account of Hypnoticks.
1. Asto the first of these, that is to say, that it may appear how Opiates work upon * 1.4 the animal spirits whilest they lay them to sleep, I have given my opinion largely in another place; and I have reason to believe, that they do not exert their force, by raising vapours into the head, nor opening the pores of the Brain, in order to admit any vaporous or otherwise soporiferous matter, but onely by deadning or defeating