582 PHILOSOPHICAL TRANSACTIONS. [aNN0 1733. 



the axis, carries along with it what should be laterally secerned. Hence a 

 paucity of animal spirits in short-necked people, who by this make are liable to 

 apoplexies, palsies, comas, lethargies, listlessness, inactivity, and drowsiness, 

 especially after meals, when the fresh chyle has got admission, to absorb a part 

 of the already few remaining spirits, which must be recruited in sleep. 



Again, in hot climates, a continual waste or dissipation of the spirits by heat, 

 makes the inhabitants generally lazy and inactive: in such the recent cliyle, the 

 grossest circulating fluid of the whole body, will quickly absorb the few remain- 

 ing spirits, and dispose them to sleep after every meal : except when the cool 

 of the evenmg checks perspiration, and the evaporation of those spirits wliich 

 were recruited by sleep in the day-time, and therefore remain plentiful enough 

 to support their activity after supper, when the business of the meaner, and 

 diversions of the richer sort, begin ; which, in colder climates, is the case after 

 breakfast and diimer. 



For a further contirmation of this, brandy, and the spirits of fermented 

 liquors, are known to produce a drowsy stupidity in such as drink them to any 

 pitch, and an habitual dulness in habitual drinkers of them ; and, when drunk 

 to excess, throw the drunken into a kind of lethargic sleep for some time. Yet 

 the quantity taken down, sufficient to produce these effects, is never so much 

 as to load or distend the stomach, so as to oppress the aorta descendens, or to 

 hinder the circulation downwards; and therefore cannot be supposed to produce 

 sleep or sleepiness in that manner, but in a different way, which shall be de- 

 scribed in the sequel of this discourse. 



Thus this position, concerning what has been generally esteemed a mechani- 

 cal cause of sleep after meals, being sufficiently refuted, it remains to endeavour 

 to establish such a general cause of sleep, as may be conformable to what is ad- 

 vanced in the essay under consideration. 



And here it will hardly be denied, that the cause of sleep in general, is a want 

 of a sufficient quantity of animal spirits for the use and exercise of the animal 

 functions : therefore whatever prevents their recruit, hinders or impedes their 

 secretion, and absorbs or fetters them when produced ; and whatever exhausts 

 or evaporates them, by occasioning a paucity of spirits, will, in a healthy per- 

 son, produce a listlessness, laziness, a tendency to sleep, or sleep itself, in pro- 

 portion to that paucity of the remaining spirits. 



If we enumerate all the known remote causes of sleep or sleepiness, we shall 

 find that in some one or other of the ways abovementioned, they all tend to 

 produce this immediate or proximate cause, viz. an impairment of the nervous 

 fluid, or animal spirits, and so bring on these several dispositions to sleep, or 

 sleep itself. 



