Magendie on Absorption. 299 



duced therefrom, I should even then, only have ex- 

 plained the absorption of substances which are soluble 

 in our humours ; gases and vapours cannot be submit- 

 ted to capillary attraction, and yet, every one knows that 

 these bodies are absorbed, and that often, with great rapidi- 

 ty. An animal plunged into sulphuretted hydrogen gas>, 

 and immediately withdrawn, is often struck with death. I 

 have seen rabbits die fron a single inspiration of prussic va^^ 

 pour. How can these phenomena be explained i* 



To understand them, we must remember that the mem- 

 branes of animals seem to offer but a feeble resistance to 

 the free circulation of the gases and vapours. Blood con- 

 tained in a bladder, reddens at its surface as though it were 

 in immediate contact with oxygen gas; pure hydrogen gasj 

 confined in a bladder, promptly acquires its detonating qual- 

 lity, if the bladder remain exposed to the atmosphere. On 

 the other hand, we are acquainted with many physiological 

 facts in which the living membranes conduct in the same 

 manner. The venous blood reddens in the lungs, when it is 

 separated from the air only by the vascular membrane ; the 

 same effect is produced in the gills of fishes. The beauti- 

 ful experiments of Mr. Eldwards have recently proved that 

 the skins of certain reptiles offer a phenomenon entirely an- 

 alagous. 



I have myself lately proved that, in birds and young mam- 

 rniferous animals, the blood reddens, and assumes the arte- 

 rial qualities, in the jugular vein when uncovered and ex- 

 posed to the air, if the precaution be taken to slacken the 

 circulation by a slight pressure on the lower extremity (ex- 

 tremite cardiaque) of the vein. 



It appears, therefore that the absorption of the gases and 

 vapours, should be attributed to the permeability of the liv- 

 ing membranes to those bodies. The theory of that per- 

 meability is not yet well understood, notwithstanding the ef- 

 forts of some celebrated men, such as Priestly and Dalton j 

 but here physiology must stop, and depend for its future 

 progress, on the advances of physical science. 



