590 OF RESPIRATION. 



775. The Lungs are capable, under peculiar circumstances, of absorbing 

 fluid from the atmosphere. Thus Dr. Madden* has shown that, if the vapour 

 of hot water be inhaled for some time together, the loss by exhalation is found 

 to be so much less than usual, as to indicate that the cutaneous transpiration 

 is partly counterbalanced by pulmonary absorption; the pulmonary exhalation 

 being at the same time entirely checked. It is probable that, if the quantity 

 of fluid in the blood had been previously diminished by excessive sweating, 

 or by other copious fluid secretions, the pulmonary absorption would have 

 been much greater. Still in the cases formerly mentioned ( 678), in which 

 a large increase in weight could only be accounted for on the supposition of 

 absorption of water from the atmosphere, it seems probable that the cutaneous 

 surface was chiefly concerned: for it can only be when the air introduced into 

 the lungs is saturated with watery vapour, that the usual exhalation will be 

 checked, or that any absorption can take place. 



776. That absorption of other volatile matters diffused through the air is, 

 however, continually taking place by the lungs, is easily demonstrated. A 

 familiar example, is the effect of the inhalation of the vapour of Turpentine 

 upon the urinary excretion. It can only be in this manner that those gases 

 act upon the system, which have a noxious or poisonous effect, when min- 

 gled in small quantities in the atmosphere. Of these, Sulphuretted Hydrogen 

 is one of the most powerful in its action ; for it has been found that air im- 

 pregnated with l-1500th part of it, will kill a bird in a very short time ; and 

 that a quantity but little more than double, namely l-800th part, will soon kill 

 a dog. This gas is exhaled in large quantities from many forms of decom- 

 posing animal and vegetable matter ; and it has recently been shown (by Pro- 

 fessor Daniell) to be absorbed by the water of the estuaries of those African 

 rivers, whose mouths are regarded as among the most pestilential spots upon 

 the surface of the globe. Carburetted hydrogen is another gas whose effects 

 are similar ; but a larger proportion is required to destroy life. Carbonic 

 acid gas, also, appears to be absorbed by the lungs, when a large proportion 

 of it is contained in the atmosphere. The accumulation of this gas in the 

 blood, when the respired air is charged with it even to a moderate amount, 

 might be attributed to the impediments thus offered to its ordinary exhalation : 

 but the following experiment appears to prove, that it may be actually absorbed 

 into the blood ; and that it will thus exert a real poisonous influence, and not 

 merely produce an asphyxiating effect. It was found by Rolando, that the 

 air-tube of one lung of the land-tortoise may be tied, without apparently 

 doing any material injury to the animal, as the respiration performed by the 

 other is sufficient to maintain life for sometime ; but, having contrived to make 

 a tortoise inhale carbonic acid by one lung, whilst it breathed air by the other, 

 he found that the animal died in a few hours.t Cyanogen is another gas 

 which has an actively-poisonous influence upon animals, when absorbed into 

 the lungs ; its agency, also, is of a narcotic character. 



777. It is singular that the effects of the respiration of pure Oxygen should 

 not be dissimilar. At first, the rapidity of the pulse and the number of the 

 respirations are increased, and the animal appears to sufler little or no incon- 

 venience for an hour; but symptoms of coma then gradually develop them- 

 selves, and death ensues in six, ten, or twelve hours. If the animals are 



* Prize Essay on Cutaneous Absorption, p. 55. 



f" The fat;il result of breathing the fumes of charcoal is, therefore, not simple asphyxia, 

 such as would result from breathing hydrogen or nitrogen. Other volatile products are set 

 free in the combustion of charcoal, besides carbonic acid. Mr. Coathupe (loc. cit.) states 

 these to be Carbonate, Muriate and Sulphate of Ammonia, Carbonic Oxide, Oxygen, Nitro- 

 gen, Watery vapour, ami Empyreumatic Oil: to these Sulphurous acid may appear to be 

 properly added. 



