REVERY, AND TRANCE. 



271 



company sleep and dreaming. The entire study is higiily interesting, 

 but requires close attention, in order to its being fully comprehended. And 

 when we have advanced thus far, we shall obtain a clue, if I mistake not, 

 to those equally abstruse and intimately connected subjects, sleep-walking, 

 revery, and winter-sleep; as well as to various other obscurities that 

 ramify from the same source. 



The fibres distributed over the moving organs of animals, I have already 

 had occasion to observe, in a preceding lecture,* are of two sorts : those 

 of the nerves, which are called sensitive fibres, and those more properly 

 belonging to the muscles, which are called irritative fibres; which last, 

 however, are always accompanied by a greater or less number of the 

 former ; by which, indeed, they become endowed with the sense of touch, 

 as well as are rendered capable of contributing to the other external 

 senses, and of maintaining a communication with the brain, from which 

 the sensitive fibres issue, or in which they terminate. 



Both these kinds of fibres become fatigued, exhausted, and torpid, in 

 proportion to the length and violence of their exertion, and recover their 

 power alone by rest. The weariness and flaccidity of the muscles of 

 the arms or legs after extreme exercise, or exercise to which they have not 

 been accustomed, may be adduced as a suflicient proof of the truth of 

 this position.! In like manner, we neither hear, nor see, nor taste, nor 

 feel, with the same accuracy, after any or all the organs of these various 

 functions have been long upon the full stretch of action, with which we 

 do on their first exertion in the morning. Increase or prolong this action, 

 and their power will be still farther obtunded, till at length, like an over- 

 wearied hmb, they become perfectly inert and insensible, and give no ac- 

 count of whatever is passing around us ; and it is this general torpitude 

 or inaction of all the external senses, which we call sleep. By the ex- 

 ercise of the will, or by any other strong stimulus, this sleep or sensorial 

 torpitude may be postponed ; and, vice versa^ by the consent of tlie will, 

 it may be accelerated. 



This, however, is sleep in its first or simplest shape alone : it is that 

 which I shall take leave to call slumber, and is the mere sleep, or torpi- 

 tude of the organs of external sense ; the will being drowsy, indeed, but 

 still continuing in some degree awake : whence the sleeper, if he lie or sit 

 in any uneasy position, exercises his muscles, which are still under the 

 control of the will, and the position is changed. The other internal 

 senses also, as those of memory, imagination, and consciousness, are in 



* Ser. I. Lect. X. 



t The principles of the theory here advanced were first given to the world by the author 

 as far back as 1805, in the comtnent subjoined to his Translation of Lucretius, where the 

 poet is treating- of the cause and pbaenomena of sleep ; and may be found in vol. ii. p. 137 — 

 141. of that work. Several of the doctrines there laid down have been since advanced in 

 various forms by different writers, though in some cases, very probably, without their having 

 perused his explanation. Thus the immediate cause of sleep, advanced in the present ipassage, 

 is that chiefly rested upon by the author of the article on sleep in Dr. Rees*s Cyclopaedia, 

 though he also adverts to an occasional increased action in the vessels of the brain as a con- 

 current cause c And thus much of the explanation which will here be found to follow, re- 

 tipenting the nature and phenomena of dreaming, have still more lately been offered to the 

 world by Dr. Spurzheim, and adopted from him by Mr. Carn>ichael of Dublin, with the ex- 

 ceptit>n that they have interwoven such views with their peculiar doctrine of a plurality of 

 organs in the brain ; which, for reasons that will be given in a subsequent Lecture, (Ser IIL 

 Lect. XIII ) the present author cannot admit ; and does not conceive is by any means ne- 

 cessary on the present occasion. Such coincidences of opinion, however, and especially if 

 they should be accidental, and not derived from his comment on Lucretius, give a considera- 

 ble degree of confirmation to the general basis on which the theory rests. The liecturCj as 

 now published, was deliyered in the spring of 1811, 



