Observations on man, his frame, his duty, and his expectations : In two parts. Part. I. Containing observations on the frame of the human body and mind, and on their mutual connexions and influences. Part. II. Containing observations on the duty and expectations of mankind / by David Hartley.

  • David Hartley
Date:
1791
Catalogue details

Licence: Public Domain Mark

Credit: Observations on man, his frame, his duty, and his expectations : In two parts. Part. I. Containing observations on the frame of the human body and mind, and on their mutual connexions and influences. Part. II. Containing observations on the duty and expectations of mankind / by David Hartley. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    abatement in the other parts, becaufe the vibrations raifed in thcfe regions during fleep, by fuch of their caiifes as take place then, will be hindered from diffufing themfelves freely, and abating their own force thereby, as foon as the other regions are collapfed and comprefled. Thefe caufes are, firft, the heat of the blood, and puliation of the arteries of the medullary fubftance j both which, when increafed on any account, mud farther increafe themfelves by a refleded influence, fince both increafe the force of the heart. Secondly, the fulnefs and diftention of the lungs. Thefe arife from the rarefadion of the blood, and accumulation of it in the veins jufl: before fleep (at w'hich time refpiration is languid), and mufl: at laft ftimulate the organs of refpiration to a vigorous exertion of themfelves, i. e. raife vigorous vibrations in the region of the brain correfponding thereto, juft as in the cafes of fighing, and recovering from the night-mare. Thirdly, we may fuppofe, that the heart, and mufcles of refpiration, do not exert themfelves during vigilance, with a degree of force at all approaching to their utmoft powers, as the limbs do; and therefore, that they, and the correfponding regions of the brain, may be qualified for a vigorous exertion during fleep. Fourthly, an increafe in the force of refpiration muft alfo increafe the force with which the heart moves, becaufe it propels the blood in greater quantities upon the heart. Fifthly, an increafe of force in the heart muft increafe both itfelf, and the adion of refpiration, becaufe the blood veflfels of the heart and organs of refpiration are particularly near to the heart, and therefore muft be particularly under its influence. Corollary i. By laying together what has been delivered concerning fleep, in this propofition, the difference between the ftates of fleep and vigilance may be thus fet before the reader, in one view. In fleep, the nerves of the five external fenfes are indifpofed to receive vibrations, and the objeds themfelves are either abfent, or impreflfed feebly. The nerves of the ftomach and bowels fympathize with thefe at firft, but recover themfelves at the inftant of fleep, the impreflions of the aliment, &c. being then made with unufual vigour; and this continues during the time of fleep. In like manner the mufcular fyftem becomes inadive in general; the heart, hov/ever, and mufcles of refpiration, are excepted, and even exert themfelves with an extraordinaiy degree of force. The blood is rarefied fo as to take up more fpace upon the whole; and as there is more in the veins, and particularly in thofe of the brain, and fpina] marrow, than in a ftate of vigilance, the medullary fubftance is hereby expofed to a conftant uniform compreffion; whereas, in vigilance, the adion of the mufcles fqueezes the blood out of the veins, and cools it, unlefs this adion be violent, or long continued. The glands are filled during fleep, and confequently, by drawing off from the fulnefs of the blood velfels, prepare the body for vigilance, and are themfelves fitted for the fundions to be then performed, i. e. to excrete their proper fluids from mufcular com- preffion, or vibrations running up their excretory duds, in the manner to be hereafter explained. The medullary fubfi 'f* Is, in like manner, fitted and prepared for vigi- lance, whether it be of a glandular nature, or not, liowever, feme vibrations muft F take
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