169 



ing$ such are the phenomena which attend the application of cupping 

 glasses. 



The pressure of the air, on the surface of the globe is necessary to the 

 existence of bodies in the condition in which we see them. Several very 

 volatile fluids, as alcohol and ether, would become gaseous, under a less 

 pressure of ^ie atmosphere; water would boil, under eighty degrees 



strength by the use of spirituous liquors, which are pure combustible matter mixed 

 with water. 



Hut in the elevated regions of the atmosphere where there is a deficiency of oxygen, 

 the fatigue which comes on is of an opposite kind. It arises from an over-propwtion of 

 combustible matter, and a want of oxygen* ^Here, of course, it is alleviated by rest, and 

 deep inspirations, and exacerbated by exercise and spirituous liquors. 



It is suddenly induced, because the pulmonary system is so contrived, that the body 

 at no instant receives more oxygen than what at the instant it requires. We are in- 

 structed by experiments, that animals placed in a vessel filled with oxygen, and respir- 

 ing the gas in a state of purity, do not consume more of it than when combined with 

 irrespirable gas. Thus, it takes an animal nearly four times as long-, to consume the 

 same quantity of oxygen as atmospheric air. 



It is speedily removed, because, by the deep inspirations the necessary quantity of 

 oxygen is conveyed into the system. 



It is accompanied by sickness of stomacJi, and loatldng of food, because, digestion, like 

 exercise, demands a copious supply of oxygen. There are many facts to prove, that 

 oxygen is a principal agent in digestion and assimilation. The quantity employed in 

 these processes seems, in some degree, to be regulated by the kind of food used. An 

 animal diet consumes more than a vegetable one. Mr. Spalding found that when he 

 lived upon animal food, and drank spirituous liquors, he expended the oxygenous por- 

 tion of the atmosphere in his diving bell, in a much shorter time than when he subsisted 

 on vegetable matter and water. Dr. Beddoes has also furnished some curious facts, 

 which go to establish the same conclusion. 



It is attended by excessive tMrst, because, in a rare atmosphere, there will, of necessity, 

 be a profuse evaporation from the surface of the body. 



The pulsations of the heart are more numerous, because they are performed less vigo- 

 rously. 



Not altogether dissimilar in its nature, or origin, though milder in its symptoms, and 

 slower in its occurrence, is the fatigue occasioned bv immoderate exercise under the 

 ordinary constitution of the atmosphere. In this case, we observed an increased fre- 

 quency of the pulse, and of respiration, &c. &c. The cure, likewise, is by rest. Cold 

 water is found more refreshing than spirituous liquors. 



There is another phenomenon connected with the present subject, which deserves 

 to be noticed. 1 allude to the propensity to sleep which has already been remarked. 

 This, too, can only be explained by ascribing it to a deficiency of oxygen. 



Sleep is a suspension of all or a majority of the operations of the mind. We have 

 not, it is true, in our possession any direct evidence to prove that the efiorts of the in- 

 tellect, like those of the body, exact a fixed and determinate quantity of oxygen. We 

 had, indeed, the promise of some experiments to ascertain it by Lavoisier, in an essay, 

 where, after indicating the expenditure of vital air by muscular exercise, he undertakes 

 to show by calculation, "the quantity of mechanical labour exerted by the philosopher 

 who refects, by the man of letters who writes, or the musician who composes.' These 

 operations, he adds, though intellectual, have a certain dependence on the physical 

 and material part of man, which renders them susceptible of comparison with the la- 

 bours of the mechanic. 



Whether these views be just as they are brilliant, I shall not pretend to decide. But, 

 though we may never be competent to determine, with much accuracy, the quantity of 

 oxygen consumed by the operations of the mind, yet, that it is essentially necessary to 

 the exertion of the intellectual faculties is sufficiently probable. 



With respect to the influence of a subtraction of oxygen in the production of sleep, 

 a few facts will be sufficient to attest it. 



In the first place, we know that the primary operation of all the irrespirable gases, 

 and these contain no oxygen, is productive of heaviness and sleep. 



Sleep is apt, moreover, to occur during the progress of digestion, when the oxygen 

 of the system is employed, in a considerable degree, in the assimilation of aliment, and 



