VOL. XXXVIII.] I'HILOSOPHICAL TKANSA.C TIONS. 581 



and therefore, according to this hypothesis, oiighit to produce the quietest and 

 most serene repose in sleep, do, on the contrary, bring inquietude, or broken 

 and interrupted rest ; and when to the greatest excess, a lethargic sleep, which 

 is a disease for the time, and sometimes terminates in death. 



The incubus also, which is justly supposed to arise from an inflation or dis- 

 tention of the stomach, in a supine posture in bed, oppressing the aorta descen- 

 dens, ought to produce quiet rest ; whereas nothing disturbs more, as it first 

 brings the person out of quiet sleep into a sort of waking dream, with a sense 

 of oppression, and at last awakes him quite, in a kind of terror, with palpita- 

 tion of the heart. 



And indeed as nothing contributes more to sound and quiet rest,- than an 

 easy digestion and respiration, a sedate, equal, and regular circulation of the 

 blood ; that is, an uninterrupted function of all the natural and vital parts : the 

 reverse of these, and particularly an interrupted or difficult circulation, if to 

 any considerable pitch, must produce the contrary effects, viz. restlessness or 

 inquietude of some kind or degree ; as in fever and other distempers attended 

 with such irregularities of the animal economy. 



The difficulty which is suggested about the chyle's not getting soon enough 

 into the blood, by the way of the lacteals, to produce this efFect in such as 

 sleep immediately after a plentiful meal, vanishes when we consider, that this 

 very rarely happens, at least never attends temperate people, in perfect health, 

 and in a temperate climate ; but such as are gross feeders, drunkards, corpu- 

 lent, short-necked, by constitution or make liable to apoplexy or palsy, or have 

 formerly suffered by such distempers, or live in a hot country. 



In gross feeders, drunkards, and such as are corpulent, from these causes the 

 lacteals are never quite empty ; in such, the food of the present meal, by 

 exciting the peristaltic motion, will, in a few minutes, press forward the chyle 

 of the preceding meal into the blood. In full vessels or tubes, the reception 

 and discharge will be instantaneous, or nearly such ; because supposing the 

 apertures to be free or unobstructed, as much precisely will issue at one extremity 

 of a full vessel or tube, as is forced into it at the opposite extremity ; and that 

 instantaneously, because of the contiguity of the globules, or particles of the 

 fluid it contains. 



In short-necked people, the passage between the heart and the brain being 

 proportionally short, the force or momentum of the circulation in the brain, is 

 by so much the greater ; but a strong and swift circulation is an enemy to all 

 secretions, as is evident in fevers, and mechanically demonstrable -, for ail the 

 secretions being by lateral branches going off at or nearly right angles, v\hich is 

 very remarkable in the brain, a swift circulation or motion along, or parallel to 



