534 OF ABSORPTION. 



571. Not only exhalation, but also (under peculiar circumstances) absorption 

 of fluid may take place through the Lungs. Thus Dr. Madden 1 has shown that, 

 if the vapour of hot water be inhaled for some time together, the total loss by 

 exhalation is so much less than usual, as to indicate that the cutaneous trans- 

 piration 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 ( 469), 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 vapor, that the usual exhalation will be 

 checked, or that any absorption can take place. 



572. 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 vapor 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 mingled in 

 small quantities in the atmosphere; and it is most astonishing to witness the 

 extraordinary increase in potency which many substances exhibit, when they 

 are brought into relation with the blood in the gaseous form. The most re- 

 markable example of this Idnd is afforded by Arseniuretted Hydrogen, the in- 

 spiration of a few hundredths of a grain of which has been productive of fatal 

 consequences, the resulting symptoms being those of arsenical poisoning. Next 

 to this, perhaps, in deleterious activity, is Sulphuretted Hydrogen ; but it would 

 seem that the effects of this upon the Human subject are scarcely so violent as 

 they are upon animals ; for though it has been found that the presence of 

 l-1500th part of it in the respired air will destroy a bird in a very short time, 

 that l-800th part suffices to kill a dog, and that l-250th part is fatal to a horse, 

 yet M. Parent-Duchatelet has affirmed that workmen habitually breathe with 

 impunity an atmosphere containing one per cent., and that he himself has re- 

 spired, without serious symptoms ensuing, air which contained three per cent. 

 There can be no doubt, however, that the continued inhalation of air thus contami- 

 nated, would be speedily fatal. Sulphuretted hydrogen and Hydro-sulphuret of 

 ammonia are given off from most forms of decaying animal and vegetable matter ; 

 and it is undoubtedly to the accumulation of these gases, that the fatal results 

 which sometimes ensue from entering sewers are to be chiefly attributed. 

 Carburetted hydrogen is another gas whose effects are similar ; but a larger pro- 

 portion of it 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 atmo- 

 sphere. 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 impedi- 

 ment thus offered to its ordinary exhalation ( 56) : 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 asphyxiat- 

 ing 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 some 

 time ; 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. 2 



1 "Prize Essay on Cutaneous Absorption," p. 55. 



2 The fatal 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 



